HK1110445A - Enhanced beacon signaling method and apparatus - Google Patents

Description

Enhanced beacon signaling method and apparatus

Technical Field

The present invention relates to communication systems, and more particularly, to a method and apparatus for transmitting information in a multi-user communication system.

Technical Field

Multiple access communication systems are common today. In these systems, multiple devices (e.g., wireless terminals) are able to communicate with a base station at the same time. Multiple-access communication systems are typically implemented as cellular systems, where each cell typically corresponds to a single base station coverage area. A cell may include one or more different sectors. In the case of sectorization, the base stations typically include different transmitters for different sectors. Further, different sectors may use the same or different carrier frequencies.

Spread spectrum OFDM (orthogonal frequency division multiplexing) multiple access is an example of a spectrum efficient wireless communication technology. OFDM can be used to provide wireless communication services. In an OFDM spread spectrum system, the entire spectral bandwidth is typically divided into a number of orthogonal tones, e.g., subcarrier frequencies. In cellular networks, the same bandwidth is often reused in all cells of the system.

In various multiple-access communication systems, transmitter information, e.g., information indicating the carrier used by a particular transmitter, cell identification information, and/or sector identification information, needs to be communicated to the wireless terminal. Transmitting such information at very high power increases the likelihood that the transmitted information will be detected, but this will result in excessive and/or unnecessary interference, say in cells or sectors that are several cells apart from the transmitter. The use of high power to transmit the transmitter information signal also limits the amount of data that can be transmitted in the system because the power allocated to transmitting the transmitter information signal is not available for transmitting user data, such as text, video or voice data.

In view of the discussion, it should be appreciated that there is a need for a method and apparatus that addresses the problem of communicating transmitter information in a reliable and easily detectable manner, while limiting the amount of signal interference generated by signals used to transmit such information and balancing the need to allocate power to such transmissions with the importance of allocating power to user data transmissions.

Disclosure of Invention

Methods and apparatus are described for implementing a communication system (e.g., an OFDM communication system) in which transmitting transmitter information (e.g., transmitter cell, sector, and/or carrier frequency information) is important in addition to user data. In accordance with the present invention, narrow band, relatively high power tones (tones) are used to transmit transmitter information. These signals are referred to herein as beacon signals. The beacon signal is transmitted at a transmission power that is several times the transmission power used to transmit other signals (e.g., user data, communication segment assignment information, etc.). In accordance with some embodiments of the present invention, a beacon signal is distinguished from a non-beacon signal by the power per tone of at least several times the power per tone of a signal transmitted at the next highest transmission power level. More specifically, beacon signals according to the present invention are transmitted using N times the power of a second highest power signal transmitted by the transmitter used to transmit the beacon signal, where N is at least 10, 20, 30, 40 or more.

By maintaining the relative difference, e.g., 20, 30, 40 or more times, between the average per tone signal energy of the user data and/or other control signals and the average per tone signal energy of the beacon signals, the probability that a beacon signal transmitted as a higher power signal is reliably detected is several times the probability that data or other control signals are detected. This approach provides a high probability of beacon signal detection while avoiding putting all or 80% or more of the available transmit power on the beacon signal. The transmit power not devoted to the beacon signal may, and in various embodiments is, used to transmit user data in parallel with the beacon signal. Thus, user data may receive more than 20%, and sometimes even more than 40% or 60%, of a transmitter's maximum possible transmit power over a period of time, e.g., a single symbol transmission period, during which a beacon signal (e.g., beacon tone) is transmitted in accordance with the present invention.

In accordance with the present invention, each base station sector transmitter transmits signals in parallel using multiple tones, e.g., more than 10, and sometimes more than 20, 100, 1000 or even more parallel tones. In some embodiments, these tones are evenly distributed in the frequency band used by a particular base station sector transmitter. As described above, more power is concentrated on the tones used to transmit the beacon signal than on other tones (e.g., used to transmit user data or other information), and it is not economical to use all or most of the base station sector transmit power for one or more tones comprising the beacon signal during a signal transmission period (e.g., an OFDM symbol transmission period). The various methods of the present invention address this challenge by using a novel mechanism for allocating power to beacon signals, thereby efficiently utilizing power while providing high detection probability.

In accordance with the present invention, in some embodiments, no more than 80% of the total available transmit power of the transmitter is devoted to beacon signals. In such embodiments, user data and beacon signals are transmitted simultaneously, e.g., using different tones, with more than 20% of the total maximum possible transmit power being allocated to user data at the time of beacon signal transmission. The beacon signal may be transmitted in the same or different frequency band as the user data (user data is transmitted simultaneously with the beacon signal). The maximum possible transmit power corresponds to a physical limit of the transmitter or a maximum set amount of power that the transmitter can use.

Thus, to efficiently utilize the available bandwidth and available transmit power, in some, but not all embodiments, during transmission of a beacon signal, more than 20% of the transmitter's power, and in many cases more than 30%, 40%, 50%, 60%, and sometimes even more than 70%, of the transmitter's total transmit power, is allocated for transmission of user data, while one or more tones corresponding to the beacon signal are also transmitted, in accordance with the present invention. Where a large number of tones are used, the beacon tone power may still be many times, e.g., 20, 30, 40 or more times, the maximum average energy per tone of the data tones occurring over a time period, e.g., a 1 second time period, which may occur anywhere in a transmission time period greater than 2 seconds, e.g., a beacon tone may be transmitted over a 2 second time period.

By limiting the number of beacon signals to a relatively small number, e.g., 1/5 or even 1/20, which is less than the number of tones used during a symbol transmission period, power can be allocated to the transmission of user data (e.g., voice, text, or image data) during any one symbol transmission period, while meeting the relatively high transmission power level requirements of the beacon signals. This approach is particularly effective in those systems that use a large number of tones, e.g., over 100, 500 or even 1000 tones in parallel, e.g., during each character transmission period. In some such OFDM embodiments, some user data is transmitted in modulated symbols on tones that are not used to transmit beacon signals during the transmission time period in which they are transmitted.

Given that beacon signals are transmitted using relatively high power levels, these signals can be detected using relatively simple methods of achieving energy detection even in the absence of maintaining precise time and tone synchronization between the beacon signal transmitter and the beacon signal receiver. Accurate detection of transmitted user data, assuming it is transmitted at a lower power level, may and often does require the receiver to achieve symbol timing synchronization with the transmitter in terms of symbol timing.

In various embodiments, the beacon signal is used to communicate transmitter information, such as a cell identifier, a sector identifier, and/or transmitter-related frequency band information used to transmit the detected beacon signal. In most embodiments, this information is transmitted by the beacon signal without regard to the beacon signal phase.

In some, but not all embodiments, a base station transmitter, e.g., a sector transmitter of a base station, transmits a signal, e.g., an OFDM symbol transmission time period, during a first time period, the signal including a number of signal tones, each signal tone corresponding to a different frequency. In one such embodiment, the transmitted signals include a beacon signal transmitted on at least one tone and a user data signal transmitted in parallel, e.g., at the same time, the tone used by the beacon signal is not used to transmit the beacon signal. In a different embodiment using this method, the average per tone power used by the transmitter to transmit user data is less than 1/20 of the per tone transmit power used to transmit the beacon signal. The beacon signal may be transmitted into a frequency band used by the transmitter to communicate user data (e.g., text, voice, or images) or into a frequency band used by an adjacent sector or cell transmitter to transmit user data.

In some embodiments, a method of operating a base station comprises the steps of: transmitting a first signal to a first region using a set of N tones over a first time period to convey information, the first time period being at least 2 seconds long, where N is greater than 10 (in some cases more than 20, 100, or 1000); transmitting a second signal comprising a set of X tones to the first region for a second time period, wherein X is less than 5 (in some cases X equals 1), and less than 80% (in some embodiments less than 60%) of the maximum average total base station transmit power used by the base station transmitter to transmit signals to the first region is allocated to the set of X tones for any one 1 second period in the first time period, and each of the X tones for which power has been allocated receives at least 20 times (sometimes at least 30 or 40 times) the average power per tone allocated to the plurality of tones during the any one second period.

Various embodiments of the present invention also relate to a base station implementing the above invention. In some exemplary embodiments, the base station includes: a transmitter that transmits information to a first region using a set of N tones, where N is greater than 10 (in some cases greater than 20, 99, 1000); a first control module connected to the transmitter for controlling the transmitter to transmit a first signal to a first area for a first time period, the first time period being at least 2 seconds long; a second control module coupled to the transmitter for controlling the transmitter to transmit a second signal in a second time period into the first region, the second signal comprising a set of X tones, wherein X is a positive integer less than 5 (equal to 1 in some embodiments), and wherein the base station transmitter allocates less than 80% of a maximum average total base station transmit power used to transmit signals in the first region during any 1 second in the first time period to the set of X tones, and wherein each of the X tones is allocated at least 20 times (sometimes at least 30 or 40 times) a maximum average power per tone allocated to the plurality of tones during any 1 second in the first time period.

In some embodiments, user data is transmitted while transmitting the beacon signal by allocating more than 20% (in some cases more than 40% or even 60%) of the maximum transmitter power to the user data. For example, during a symbol transmission period, the sector transmitter devotes 40% of the maximum allowed output transmit power to transmission. The beacon signal is transmitted on a tone during the same transmission period, the beacon tone being transmitted at a power level that exceeds 20 times the power level of the user data, or 40 or 60 times in some cases.

The method and apparatus are well suited for OFDM implementations where multiple modulation symbols (one modulation symbol transmitted per tone) are transmitted in parallel within one OFDM symbol period. In these embodiments, the beacon signal may be transmitted in parallel with the tones used to transmit the data symbols.

Drawings

Fig. 1 depicts an exemplary base station transmitter timing relationship in accordance with the method of the present invention.

Fig. 2 depicts an exemplary power per tone relationship over an exemplary second time interval.

Fig. 3 depicts another exemplary power per tone relationship over an exemplary second time interval.

Fig. 4 depicts another exemplary power per tone relationship over an exemplary second time interval, which corresponds to an embodiment in which the second time interval and the third time interval completely overlap.

Fig. 5 depicts an exemplary power per tone relationship over an exemplary fifth time interval.

Fig. 6 depicts an exemplary base station transmitter timing relationship in accordance with the method of the present invention.

Fig. 7 depicts another exemplary power per tone relationship over an exemplary second time interval, which corresponds to an embodiment in which the second time interval and the third time interval completely overlap.

Fig. 8 depicts another exemplary power per tone relationship over an exemplary second time interval, which corresponds to an embodiment in which the second time interval and the third time interval completely overlap.

Fig. 9 depicts an example wireless communication system that supports beacon signaling, implemented in accordance with the invention.

Fig. 10 depicts an exemplary base station (alternatively referred to as an access point) implemented in accordance with the present invention.

Fig. 11 is a schematic diagram of an exemplary wireless terminal (MT), e.g., a mobile node, implemented in accordance with and using the methods of the present invention.

Fig. 12 is a flow diagram of an exemplary method for operating a base station transmitter in a frequency division multiple access communication system (e.g., an OFDM system) in accordance with the present invention.

Fig. 13 is a flow diagram of another exemplary method of operating a base station transmitter in a frequency division multiplexed system in accordance with the invention.

Fig. 14 is a flow chart of an exemplary method of operating a base station transmitter in a communication system in accordance with the present invention.

Detailed Description

A diagram 100 in fig. 1 depicts an exemplary base station transmitter timing relationship in accordance with the method of the present invention. Fig. 1 includes a horizontal axis 102 representing time and a first period of time 104 (e.g., 2 second intervals). In some embodiments, the first time period 104 is greater than 2 seconds.

The exemplary base station transmitter (e.g., an OFDM signal sector transmitter) operates in an exemplary frequency division multiple access system (e.g., an OFDM system) to transmit a first signal to a first region (e.g., a sector of a cell) using a set of N tones for a first time period 104 to enable the transfer of information, where N is greater than 20. In some embodiments, the transmitter is a sector transmitter corresponding to a carrier frequency within a sector of a cell using multi-carrier frequencies.

The set of N tones (e.g., 113 tones) may be used for downlink signaling from the base station transmitter to wireless terminals, including broadcast signals including beacon signals and assignment information and user-specific signals, e.g., user-specific downlink traffic channel signals including user data. In an exemplary second time period 106 (e.g., one OFDM symbol transmission period), the transmitter transmits a second signal comprising a set of X tones into the first region, wherein X is less than 5, and wherein during any 1 second within the first time period, less than 80% of a maximum average total base station transmit power used by the base station transmitter to transmit signals into the first region is allocated to the set of X tones, and during the any one second, each of the X tones to which power has been allocated is allocated at least 20 times the average per tone power allocated to the plurality of tones during the first time period. For example, the set of X tones in the second time period 106 includes a beacon signal, which may be one OFDM time interval in a series of consecutive OFDM transmission time intervals that has been assigned for the beacon signal. In some embodiments, user data including at least one of voice, text and image data is communicated over at least one of the transmitted N tones during the first time period 104. During the second time period 106, transmitter information including at least one of sector information, cell information, and carrier frequency information is transmitted on at least one of the X tones. Fig. 1 shows an exemplary 1-second interval 108 of maximum average total base station transmit power used by the base station transmitter to transmit signals to the first region. In general, the one-second interval 108 of maximum power may be sliding or occur at different locations of the first time period 104. Fig. 1 includes an exemplary fifth time period 110, e.g., an exemplary OFDM symbol transmission time interval within the 1 second time interval 108.

Fig. 1 also includes an exemplary third time period 112, e.g., an exemplary OFDM symbol transmission time interval. During the third time period, the transmitter transmits a third signal to the first region, the third signal comprising a set of Y tones, where Y ≦ N, the power allocated to each tone of the third set of tones being at most 8 times the average per tone power allocated to the plurality of tones during the 1-second time period 108. In fig. 1, the third time period 112 and the second time interval 106 are the same in duration, e.g., one OFDM symbol transmission time interval. In some embodiments, the second and third time periods (106, 112) overlap. In the example of fig. 1, the second and third time intervals (106, 112) completely overlap. In some embodiments, the second and third time intervals (106, 112) are disjoint. In various embodiments, the transmitter modulates at least two of data, control, and pilot signals on at least some tones in a set of Y tones during the third time period.

In some embodiments, the transmitter transmits user data using Y tones in the second time period, the Y tones belonging to the set of N tones but not included in the X tones, where Y is a positive integer greater than 1, more than 20% of the total transmitter power used in the second time period 106 allocated to the Y tones in the second time period 106. In some embodiments, more than 50% of the total transmitter power used in the second time period 106 is allocated to the Y tones. In various embodiments, transmitting user data includes transmitting modulated symbols on the Y tones, each of the Y tones conveying one symbol, e.g., one OFDM modulation symbol within one OFDM symbol transmission time interval.

In some embodiments, an exemplary fourth time period also occurs within the first time period 104, the fourth time period being of the same duration as the second time period and non-overlapping with the second time period. For example, the fourth time period is a time interval for transmitting another beacon signal on a set of G tones, the beacon signal transmitted during the fourth time period being different from the beacon signal transmitted during the second time period.

Note that fig. 1 is not drawn to scale.

The diagram 200 of fig. 2 depicts an exemplary power per tone relationship over an exemplary second time interval 106. The vertical axis 202 of fig. 2 represents the power per tone of the second time segment 106 divided by the average power per tone over the one-second time interval 108, with the horizontal axis 204 representing the tone index. Corresponding to the example system of fig. 2, N50 tones (tone index 0.. 49)206 are used for downlink signaling. The exemplary beacon signal 208 uses a tone indexed 34 and uses 25 times the power per tone averaged over a one second time interval. Thus, in this example, tone set X contains one tone. In some embodiments, tone set X includes two tones. As shown in fig. 2, the relatively high concentration of power over narrow frequencies makes the beacon signal 208 easy to detect and identify by wireless terminals receiving downlink signaling.

The diagram 300 of fig. 3 depicts another exemplary power per tone relationship over the exemplary second time interval 106. The vertical axis 302 of fig. 3 represents the power per tone of the second time segment 106 divided by the average power per tone over the one-second time interval 108, with the horizontal axis 304 representing the tone index. Corresponding to the example system of fig. 3, N-500 tones (tone index 0.. 499)306 are used for downlink signaling. The example beacon signal 307 transmitted during the second time period 106 uses four tones with tone index values of 7, 12, 17, 21 and has a power per tone that is 25 times the average per tone power over a one second time interval, represented by blocks (308, 310, 312, and 314), respectively.

In some embodiments, at least one of the X tones, e.g., a beacon tone, is transmitted at a predetermined frequency, wherein at least one of the X tones is transmitted using a frequency that is a fixed offset ≧ 0 from the lowest frequency tone of the N sets of tones. For example, the carrier beacon signal may use the X tones. In some embodiments, at least one of the X tones is transmitted on a frequency dependent upon at least one of a base station identifier and a sector identifier.

In the example shown in fig. 2, the exemplary second signal, e.g., a beacon signal, is transmitted using the X tone set, where X ═ 1, using 50% of the maximum average total base station transmit power used by the base station transmitter to transmit signals to the first region in the 1 second time interval 108. In the example shown in fig. 3, the exemplary second signal, e.g., a beacon signal, is transmitted using the X tone set, where X-4, using 20% of the maximum average total base station transmit power used by the base station transmitter to transmit signals to the first region in the 1 second time interval 108.

In the examples shown in fig. 2 and 3, none of the N-X tones belonging to the set of N tones are used during the second time period 106, during which time the transmitter power is concentrated on the beacon signal (X tones) and not the other (N-X) tones.

The diagram 400 of fig. 4 depicts another exemplary power per tone relationship over the exemplary second time interval 106. Fig. 4 corresponds to an embodiment in which the second time period 106 and the third time period 112 completely overlap. The vertical axis 402 of fig. 4 represents the power per tone of the second time segment 106 divided by the average power per tone over the one-second time interval 108, with the horizontal axis 404 representing the tone index. In the example shown in fig. 4, the second time period 106 and the third time period 112 are the same. Corresponding to the example system of fig. 4, N-100 tones (tone index 0.. 99)406 are used for downlink signaling. During the second time period 106, the example beacon signal 408 is transmitted using one tone indexed 68 and having a power that is 25 times the average per tone power of the tones over a one second time interval. Thus, in this example, the X tone set of the beacon signal 408 includes one tone. In fig. 4, the set of Y tones includes 99 tones belonging to the set of N tones, but not belonging to the set of X tones. The tone power of the Y tone sets is 5 times, 1 times, or 0.5 times the power per tone divided by the average power per tone over a 1 second time interval. For example, an example signal 410 using tone 0 at 5 times the relative power level may be part of a pilot signal, while an example signal 412 using tone 12 at 1 times the relative power level may be part of a control signal, such as an allocation signal, an acknowledgement, a timing control signal, or a power control signal. An exemplary signal 414 using tone 99 at 0.5 times the relative power level may be part of a downlink traffic channel signal carrying user data.

The diagram 500 of fig. 5 depicts an exemplary power per tone relationship over an exemplary fifth time interval. The vertical axis 502 of fig. 5 represents the ratio of the power per tone of the fifth time segment 110 to the average power per tone over the one-second time interval 108, with the horizontal axis 504 representing the tone index. Corresponding to the example system of fig. 3, N-500 tones (tone index 0.. 499)506 are used for downlink signaling. The tones shown in the example of fig. 5 are 2, 1, or 0.5 times the power per tone divided by the average power per tone over a one second time interval. For example, the example signal component 512 uses a tone 38 at 2 times the power level, which may be part of a control signal, such as a pilot signal, an assignment signal, an acknowledgement signal, a timing control signal, or a power control signal; exemplary signal component 510 uses tone 13 at 1 times the power level, which may be part of a user data signal, while exemplary component 508 uses tone 9 at 0.5 times the power level, which may be part of another user data signal. In the exemplary fifth time interval 110 shown, the total transmit power is 100% of the average transmit power over a 1 second time interval of the maximum average total base station transmit power for the first region. In the example shown in fig. 5, two tones using the 512-type signal component account for 4% of the total power, 94 tones using the 510-type signal component account for 94% of the total power, and 4 tones using the 508-type signal component account for 2% of the total power. In summary, in each fifth time interval 110, e.g. in each OFDM symbol transmission time interval, the total power will deviate from the average power of the 1 second time interval 108.

Fig. 6 is a diagram 600 depicting exemplary base station transmitter timing relationships in accordance with the method of the present invention. FIG. 6 shows an exemplary variation of FIG. 1, in accordance with the present invention. The exemplary first time period 604 shown in fig. 6 is similar or identical to the exemplary first time period 104 shown in fig. 1. The exemplary one-second time interval 608 of the maximum average total base station transmit power shown in fig. 6 is similar or identical to the time interval 108 shown in fig. 1. The example second time period (606, 606') shown in fig. 6 is similar or identical to the example second time period 106 shown in fig. 1. The example first second time period 606 and the example second time period 606' indicate that the second time period is periodically repeated within the first time period 604. Fig. 6 includes a repetition of the third time within first time period 604 (first third time period 612, second first time period 612', third first time period 612 ",.., nth third time period 612 *). Each third time period (612, 612', 612 ", 612 *) is similar or identical to the example third time period 112 shown in fig. 1. In some embodiments, the second time period is repeated once every time the third time period is repeated at least Z times, wherein Z is at least 10. In some embodiments, Z is at least 400.

Fig. 7 is a diagram 700 depicting another exemplary power per tone relationship over an exemplary second time interval 106. Fig. 7 corresponds to an embodiment in which the second period 106 and the third period 112 completely overlap. The vertical axis 702 of fig. 7 represents the ratio of the power per tone of the second time segment 106 to the average power per tone over the one-second time interval 108, and the horizontal axis 704 represents the tone index. In the example of fig. 4, the second time period 106 and the third time period 112 are the same. Corresponding to the example system of fig. 7, N-100 tones (tone index 0.. 99)706 are used for downlink signaling. The example beacon signal 708 transmitted during the second time period 106 uses one tone with a tone index equal to 68 and is 25 times the average per tone power of the individual tones over the one second time interval. Thus, in this example, the set of X tones of beacon signal 708 includes one tone. In fig. 7, 35 tones included in the set of Y tones belong to the set of N tones, but do not belong to the set of X tones. The power per tone of the Y tone sets is 5 times, 1 times or 0.5 times the average power per tone over a 1 second time interval. For example, example signal 710 using tone 0 at 5 times the relative power level may be part of a pilot signal, while example signal 712 using tone 12 at 1 times the relative power level may be part of a control signal, such as an allocation, acknowledgement, timing control signal, or power control signal. An example signal 714 using tone 99 at 0.5 times the relative power level may be part of a downlink traffic channel signal carrying user data. Exemplary tone 26716 is a tone that is unused in the set of N tones. In this embodiment, 64 tones in the set of N-X99 tones are unused in the first region in the second time period 106. In some embodiments, at least half of the N-X tones belonging to said set of N tones but not to said set of X tones are unused in said second time period within the first region.

Fig. 8 is a diagram 800 depicting another exemplary power per tone relationship within the exemplary second time interval 106, which corresponds to an embodiment in which the second time interval and the third time interval completely overlap. Fig. 8 corresponds to an embodiment in which the second period 106 and the third period 112 completely overlap. The vertical axis 802 of fig. 8 represents the ratio of the power per tone of the second time segment 106 to the average power per tone over the one-second time interval 108, and the horizontal axis 804 represents the tone index. In the example shown in fig. 8, the second time period 106 and the third time period 112 are the same. The example system shown in fig. 8 uses N-100 tones (tone index 0.. 99)806 for downlink signaling. The example beacon signal 808 transmitted during the second time period 106 uses one tone with a tone index equal to 68 and a power per tone over a one second time interval that is 25 times the average power per tone. Thus, in this example, the set of X tones of the beacon signal 808 includes one tone. In fig. 8, the set of Y tones shown contains two tones (tone coordinate 12 and tone coordinate 26) belonging to the set of N tones but not to the set of X tones, which correspond to signal components (812, 812'), respectively. In this example, the power per tone of the Y tone sets is 1 times the average power per tone over a one second time interval. An example signal 812, for example using tone 12 at 1 times the relative power level, may be part of a control signal, such as a pilot, allocation, acknowledgement, time control, or a power control signal or part of a user data signal, such as a signal including video, text, and/or user application data. Example tone 26816 is an unused tone in the set of N tones. In this embodiment, 97 tones in the set of N-X99 tones are unused in the first region during the second time segment 106. In some embodiments, a plurality of tones of the N-X tones belonging to the set of N tones but not to the set of X tones are used in the first region during the second time period.

Fig. 9 depicts an example wireless communication system 900 that supports beacon signaling, implemented in accordance with the invention. The system 900 uses the methods and apparatus of the present invention. Fig. 9 includes a number of exemplary multi-sector cells: cell 1902, cell 2904, cell 3906. Each cell (902, 904, 906) represents a Base Station (BS) wireless coverage area, respectively (base station 1908, base station 2910, base station 3912). In the illustrated example embodiment, each cell 902, 904, 906 includes three sectors (a, B, C). Cell 1902 includes sector a 914, sector B916, and sector C918. Cell 2904 includes sector a 920, sector B922, and sector C924. Cell 3906 includes sector a 926, sector B928, and sector C930. In other embodiments, the number of sectors per cell may vary, such as 1 sector per cell, 2 sectors per cell, or more than 3 sectors per cell. Furthermore, different cells may include different numbers of sectors.

Wireless Terminals (WTs), e.g., Mobile Nodes (MNs), are wirelessly connected to the base station and are mobile in the system and communicate with peer nodes, e.g., other mobile nodes. In sector a 914 of cell 1902, wireless terminals (932, 934) are connected to base station 1908 via wireless links (933, 935), respectively. In sector B916 of cell 1902, wireless terminals (936, 938) are connected to base station 1908 via wireless links (937, 939), respectively. In sector C918 of cell 1902, wireless terminals (940, 942) are connected to base station 1908 via wireless links (941, 943), respectively. In sector a 920 of cell 2904, wireless terminals (944, 946) are connected to base station 2910 through wireless links (945, 947), respectively. In sector B922 of cell 2904, wireless terminals (948, 950) are connected to base station 2910 through wireless links (949, 951), respectively. In sector C924 of cell 2904, wireless terminals (952, 954) connect to base station 2910 through wireless links (953, 955), respectively.

Multiple base stations may be connected together by a network to provide connectivity for wireless terminals within a particular cell to peer terminals outside the particular cell. In system 900, base stations (908, 910, 912) are connected to network node 968 through network links (970, 972, 974), respectively. Network node 968, e.g., a router, is coupled to other network nodes, e.g., other base stations, routers, home agent nodes, AAA server nodes, etc., and the internet via network link 976. The network links 970, 972, 974, 976 may be, for example, fiber optic links.

In accordance with the present invention, base stations 908, 910, 912 include sector transmitters, each of which utilizes an assigned designated carrier frequency for ordinary signaling, e.g., downlink communication signals, such as user data directed to a particular wireless terminal. The tone frequencies allocated by the sector transmitter are used for ordinary signaling while transmitting broadcast signals, e.g., allocation signals, pilot signals, and/or beacon signals, from the base station to the wireless terminals. The base stations 908, 910 transmit beacon signals that communicate tone information, cell identification information, and/or sector identification information. Further, in accordance with some embodiments of the present invention, each base station sector transmitter transmits additional downlink signals, e.g., pilot signals and/or beacon signals within the carrier frequency bands allocated to neighboring cell/sector transmitters for their ordinary signaling. Such downlink signals provide information to wireless terminals, such as wireless terminal 932, for evaluating and deciding which carrier frequency to select and which corresponding base station sector/cell to use as an access point. A wireless terminal, such as wireless terminal 932, includes a receiver capable of processing information from a base station 908, 910, 912 sector transmitter that provides information on another carrier frequency band that may be used for ordinary communications, such as downlink traffic channel signaling, and which may be selected by the wireless terminal.

Fig. 10 depicts an example base station 1000 (also referred to as an access point) implemented in accordance with the present invention. The base station is referred to as an access point because it acts as a network access point for the wireless terminal and provides the wireless terminal with an opportunity to access the network. The base station 1000 shown in fig. 10 may be a more detailed representation of any of the base stations 908, 910, 912 of the system 900 shown in fig. 9. Base station 1000 includes a sector receiver 1002, a sector receiver 1004, a processor 1006, (e.g., a CPU), I/O interface 1008, and memory 1010, coupled together by a bus 1012 over which the various elements exchange data and information. A sector receiver includes multiple receivers (sector 1 receiver 1016, sector N receiver 1020), each coupled to a respective receive antenna (receive antenna 11018, receive antenna N1022). Each receiver (1016, 1020) includes a decoder (1024, 1026). Uplink signals from multiple wireless terminals 1100 (see fig. 11) are received through sector antennas (1018, 1022) and processed by sector receivers (1016, 1020). A decoder (1024, 1026) at each receiver decodes the received uplink signal and retrieves the information encoded by wireless terminal 1100 prior to transmission. Sector transmitter 1004 includes multiple transmitters, sector 1 transmitter 1028 and sector N transmitter 1030. Each sector transmitter (1028, 1030) includes an encoder (1036, 1038) for downlink data/information encoding and is coupled to a respective sector transmit antenna (1030, 1034). Each antenna 1030, 1034 corresponds to a different sector and transmits to the sector in which the antenna corresponds, which may be located. The antennas 1030, 1034 may be separated or may correspond to different elements of a single multi-sector antenna, with different antenna elements for different sectors. Each sector transmitter (1030, 1034) has an assigned carrier frequency band for ordinary signaling, e.g., downlink communication signaling. Each sector transmitter (1030, 1034) is capable of transmitting downlink signals, e.g., assignment signals, data and control signals, pilot signals and/or beacon signals, within a designated carrier frequency band. In accordance with some embodiments of the invention, each sector transmitter (1030, 1034) also transmits additional downlink signals, e.g., pilot signals and/or beacon signals to other carrier bands. The base station I/O interface 1008 connects the base station 1000 to other network nodes, such as other access nodes, routers, AAA servers, home agents, and the internet. Memory 1010 includes programs 1040 and data/information 1042. Processor 1006 executes routines 1040 and uses the data/information in memory 1010 to control the operation of base station 1000 in accordance with the invention, including: users are scheduled on different carrier frequencies using different power levels, power control, time control, communications, signaling, and beacon signaling.

The programs 1040 include multiple program sets (sector 1 program 1044, sector N program 1046), each set corresponding to a sector covered by the base station 1000. In some embodiments, for example, where multi-carrier frequencies are used for general signaling in a single sector, e.g., downlink traffic channel signaling containing user data, additional sets of procedures may exist as the sector corresponds to different carriers, which correspond to different base station sector access points.

Example sector 1 programs 1044 include communications programs 1048 and base station control programs 1050. The communication routines 1048 implement the different communication protocols used by the base station 1000. Base station control routines 1050 use data/information 1042 to control the operation of the base station, including the operation of sector 1 receiver 1016, the operation of sector 1 transmitter 1028, the operation of I/O interface 1008 and the implementation of the inventive methods. Scheduler module 1052 schedules users, e.g., allocates space-link resources such as uplink and downlink traffic channel segments to wireless terminals. Signaling module 1054 uses data/information 1042 in memory 1010 to control downlink and uplink signaling related to sector 1 signaling. Signaling module 1054 controls sector 1 transmitter 1028 to transmit over a time period, e.g., 2 seconds or longer intervals, using downlink signals transmitted to a first sector of a cell corresponding to base station 1000. Some transmitted downlink signals include downlink traffic channel signals that include user data such as voice, text and/or image information, pilot signals, and other control information such as allocation, acknowledgement, timing control, and power control information. Signaling module 1054 uses a set of tones allocated to base station 1000 that includes N sets of downlink tones, where N is greater than 20. The signaling module 1054 controls timing operations, e.g., OFDM symbol transmission timing operations and beacon activation timing control operations.

Beacon module 1056 includes a sector 1 beacon module 1058 and an adjacent sector beacon module 1060. In accordance with the invention, beacon module 1056 uses the data/information 1042 in memory 1010 to control sector 1 transmitter beacon functions, including beacon signal generation and transmission. Beacon module 1056 controls sector 1 transmitter 1028 to transmit a beacon signal at a scheduled beacon signaling time interval, the beacon signal using a set of X tones, where X is a positive integer less than 5, and the power allocated to the set of X tones of the beacon signal is less than 80% of the maximum average base station transmit power for the base station transmitter to transmit to sector 1 for any one 1 second time interval within a first specified time period of at least 2 seconds, the at least 2 second long time interval including the beacon signal, and wherein the power allocated to each of the X tones is at least 20 times the average power allocated to the plurality of tones per tone over any one second long time period of the at least 2 second long time interval.

Sector 1 beacon module 1058 performs control operations related to beacon signal generation and transmission in the carrier frequency band used by sector 1 transmitter 1028 for ordinary downlink signaling (e.g., downlink signaling containing user data). The adjacent sector beacon module 1060 performs operations related to beacon signal generation and transmission in the carrier frequency band used by the adjacent sector to transmit ordinary downlink signaling. By transmitting beacon signals within a contiguous frequency band, wireless terminals with a single chain receiver tuned to a single carrier can receive beacon signals that convey information about potential carrier frequency base station sector access points while operating on the current access point carrier frequency.

Data/information 1042 includes a plurality of data/information sets (sector 1 data/information 1062, sector N data/information 1064). Sector 1 data/information 1062 includes data 1066, sector information 1068, multiple sets of carrier information (carrier 1 information 1070, carrier N information 1072), tone information 1074, non-beacon downlink tone information 1076, beacon information 1078, wireless terminal data/information 1080, average transmitter power information 1082, current transmitter power information 1084, time information 1086, and downlink signals 1088.

Data 1066 includes user data/information received from and intended for a plurality of wireless terminals, e.g., wireless terminals having sector 1 of base station 1000 as a network access point, and wireless terminals engaged in a communication session with wireless terminals having sector 1 of base station 1000 as a network access point. Sector information 1068 includes information identifying sector 1, e.g., a particular base station sector identifier.

Carrier information (carrier 1 information 1070 and carrier N information 1072) includes information related to each carrier used for downlink signaling in sector 1. In some embodiments, a given sector of a cell may use multiple carriers for downlink signaling including user data, each carrier corresponding to a different network access point. In such an embodiment, each carrier within a sector may be associated with a different base station sector transmitter, and a given sector may have multiple base station sector transmitters, e.g., multiple sector 1 transmitters 1028.

In some embodiments, e.g., embodiments using adjacent sector beacon module 1060, carrier information (1070, 1072) may identify whether the carrier is the carrier with which transmitter 1028 transmits ordinary downlink signaling (containing user data, beacon signals, and other control information) in sector 1, or whether the carrier is the carrier used by an adjacent sector transmitter for user data downlink signaling in the case where the sector 1 transmitter transmits beacon signals using the carrier instead of user data.

The carrier information (1070, 1072) also includes information identifying the bandwidth, e.g., the downlink carrier is centered around. Carrier information (1070, 1072) includes information related to the downlink and/or uplink carriers used in sector 1. The downlink carrier information is used for tuning of the sector 1 transmitter 1028 and the uplink carrier information is used for tuning of the sector 1 receiver.

Tone information 1074 includes downlink tone information 1090 associated with downlink signaling for sector 1 of base station 1000 and uplink tone information 1092 associated with uplink signaling for sector 1 of base station 1000. Downlink tone information 1090 includes tone set information 1094 and power information 1096. Tone set information 1094 includes a set of N tones, where N is greater than 20, which are used by sector 1 transmitter 1028 for downlink signaling including user data, beacon signals, pilot signals, and other control signals such as allocation, acknowledgement, timing control signals, and power control signals. In some embodiments, the set of N tones is a contiguous set of tones that use the bandwidth allocated to downlink signaling by the sector 1 transmitter 1028.

In some embodiments, downlink tone information 1090 includes tone hopping information, where the information is mapped to logical tones according to a periodic predetermined tone hopping sequence that hops to physical tones over time, the tone hopping sequence being base station and/or base station sector dependent. Power information 1096 includes power level information including total sector transmit power allocated to the N tone sets, power level information on a per tone basis, and/or power information on an average basis.

Uplink tone information 1092 includes information, e.g., information related to the set of tones in the uplink frequency band to which sector 1 receiver 1016 is tuned.

Beacon packet 1078 includes tone set information 1097, power information 1095, and transmitter information 1093. Tone set information 1097 includes information for one or more X tone sets, X being less than 5, of the set of N tones, where each set of X tones includes a tone of a beacon signal. Power information 1095 includes information identifying a power level to be used by each of N tones of a beacon signal, wherein any one of X tones to which power has been allocated is allocated at least 20 times the average power per tone allocated to tones over any one second period within a first period of time that is at least 2 seconds long, said first period of time containing said beacon signal; power information 1095 also includes information identifying a power level for a combined set of X tones (including beacon signals) where the power is less than 80% of the maximum average total base station transmit power for base station sector 1 transmitter 1028 over any one second period.

Transmitter information 1093 includes cell identification information 1091, sector ID information 1089, and tone identification information 1087. The heterogeneous transmitter identification information in information 1093 may be conveyed by a beacon signal, e.g., a set of N tones associated with a beacon, when the sector 1 transmitter 1028 transmits the beacon in a repeating sequence of beacon signals.

Non-beacon downlink tone information 1076 includes information on Y sets of tones, Y ≦ N, used to transmit non-beacon downlink signals, such as user data, pilot signals, and other control signals. The Y tone sets may vary in different time intervals, e.g., different OFDM symbol transmission time intervals. For example, when a beacon signal is not transmitted within an OFDM transmission interval, the Y sets of tones may include each of the N sets of tones. In some embodiments, the Y tone sets comprise 0 tones within a beacon transmission interval. In other embodiments, within a beacon interval, there are sets of N-X tones, and a subset of Y tones of the N-X sets of tones are used to transmit user data at the same time as the beacon signal transmission. In some embodiments, the number of tones in the Y tone sets within a beacon transmission interval is greater than 50. Power information 1099 includes information identifying the power allocated to the set of Y tones and each tone in the set of Y tones. In some embodiments, more than 20% of the total sector transmitter power in a beacon transmission interval is allocated to the set of Y tones in the beacon interval. In some embodiments, more than 50% of the total sector transmitter power in a beacon transmission interval is allocated to the set of Y tones in the beacon interval.

Wireless terminal data/information 1042 includes a plurality of information sets (wireless terminal 1 data/information 1085, wireless terminal N data/information 1073). Each set of information, e.g., wireless terminal 1 data/information 1085, may correspond to a wireless terminal that uses base station 1000 sector 1 as its network access point. Wireless terminal 1 data/information 1085 includes user data 1083 routed to/from wireless terminal 1 and resource/user/session information 1075. User data 1083 includes voice information 1083, text information 1079, and image information 1077. Resource/user/session information 1075 includes information identifying the resources allocated to wireless terminal 1 (e.g., base station assigned identifiers) and the segments allocated (e.g., dedicated uplink and downlink traffic channel segments). Resource/user/session information 1075 also includes information identifying the user, e.g., other wireless terminals in a communication session with wireless terminal 1, and routing information associated with the other wireless terminals.

The average transmit power information 1082 includes information of the average transmit power of the sector 1 transmitter 1028, e.g., over a one second time interval. Current transmit power information 1084 includes information regarding the transmit power of the sector 1 transmitter 1028 within the current OFDM symbol transmission interval, including information on the power level of each tone used within the current OFDM symbol transmission interval. When the current OFDM symbol transmission interval is a beacon interval, the current transmit power information 1084 also includes information regarding the combined power of the set of tones containing the beacon signal. In accordance with the method of the present invention, the transmit power allocated to the tones is controlled, e.g., relatively high power levels are allocated to beacon tones on a per tone basis as compared to the power levels allocated to user data or non-beacon control signals on a per tone basis.

Time information 1086 includes time interval information 1071 and repetition information 1069. Time interval information 1071 includes time structure information about transmission time intervals, e.g., a time period of at least 2 seconds during which sector 1 transmitter 1028 is to transmit signals to sector 1. The interval information also includes information about the time period for which the control sector 1 transmitter 1028 transmits beacon signals to sector 1 and information about the time period for which the control sector 1 transmitter 1028 transmits non-beacon signals to sector 1. Interval information 1071 includes information such as OFDM symbol time information, e.g., duration of a single OFDM symbol transmission interval and time synchronization information, e.g., information about other sectors of a cell and between downlink and uplink.

Repetition information 1069 includes information related to the periodic repetition of beacon signals and/or beacon signaling intervals. The repetition information 1069 includes information of structure repetition, for example, a slot (group of consecutive OFDM symbol transmission intervals), a superslot (group of slots), a beacon slot (group of superslots including one beacon signal), and a minislot (group of beacon slots in which different beacon signals in the minislot include different beacon slots).

Downlink signals 1088 include OFDM modulation symbols 1067, beacon signals 1065, non-beacon control signals 1063, and user data signals 1061. OFDM modulation symbols 1067 include information transmitted on modulation symbols, such as data, control, and/or pilot information modulated on one symbol, which are transmitted using non-beacon tones. Beacon signal 1065 includes information identifying the transmitted beacon signal, e.g., a beacon signal conveying transmitter information including: carrier information, sector ID information and/or cell ID information. The non-beacon control signals 1063 include signal information such as allocation, acknowledgement, power control, timing control, and pilot signals and associated control segment information. User data signal 1065 includes information for user signals such as downlink traffic channel segment signals and corresponding segment information.

Figure 11 is a diagram 1100 of an exemplary Wireless Terminal (WT), e.g., mobile node, implemented in accordance with and using the methods of the present invention. Example wireless terminal 1100 may be any wireless terminal of example system 900 of fig. 9 (932, 934, 936, 938, 940, 942, 944, 946, 948, 950, 952, 954, 956, 958, 960, 962, 964, 966).

Wireless terminal 1100 includes a receiver 1102, a transmitter 1104, a processor 1106 (e.g., CPU), user I/O devices 1108, and memory 1110 coupled together by a bus 1112 over which the various elements exchange data and information. Memory 1110 includes routines 1136 and data/information 1138.

Processor 1106 executes programs 1136 and data/information 1138 in memory 1110 to control the operation of the wireless terminal and implement the methods of the present invention. User I/O devices 1108, e.g., microphone, keyboard, keypad, mouse, camera, speaker, display, etc., allow a user of wireless terminal to input user data/information for transmission to another wireless terminal that is engaged in a communication session with wireless terminal 1100, and to output user data received from another wireless terminal that is engaged in a communication session with wireless terminal 1100.

Receiver 1102 is coupled to receive antennas 1114 through which wireless terminal 1100 can receive downlink signals from base stations including beacon signals, user data signals, and non-beacon control signals such as pilot signals, timing control signals, power control signals, assignments, and acknowledgements. Receiver 1118 includes a first radio frequency module, a first receiver chain 1120, a digital processing module 1122, an energy detection/signal to noise ratio detection module 1124, and a band selection controller 1126. In some embodiments, e.g., some dual radio frequency receiver chain embodiments, receiver 1102 includes a second radio frequency module 1128 and a second receiver chain 1130.

The first radio frequency module 1118 tunes to the carrier signal and receives and processes downlink signals in the carrier signal band. The first receiver chain 1120 receives and processes the output signal of the first radio frequency module 1118. The first radio frequency module 1118 receives control data from the band selection controller 1126, for example, to select a carrier frequency and tune the receiver 1102 to this selected frequency.

The first receiver chain 1120 comprises an analog/digital module 1119 for performing analog-to-digital conversion and an FFT/DFT (fast fourier transform/discrete fourier transform) module 1121 for performing FFT or DFT on the digital signal output by the analog/digital module 1119. The first rf chain 1120 may include other filters, such as a baseband filter. The output of the first receiver chain 1120 is input to an energy detection/signal-to-noise ratio detection module 1124.

The energy detection/signal-to-noise ratio detection module 1124 detects energy corresponding to each tone of the downlink band. The beacon signal component is identified by a higher per tone power relative to other non-beacon tones. In some embodiments, the beacon signal may also be detected by signal-to-noise ratio measurement information. Note that beacon detection does not require precise time synchronization, e.g., beacons transmitted from multiple unsynchronized base station transmitters within the same carrier frequency band can be detected and processed.

Non-beacon components, e.g., low power tones not classified as beacon tones and transmitted from the access point base station sector, are processed by the signal digital signal processing module 1122. The digital signal processing module 1122 performs symbol detection and recovery. The operations of the digital processing module 1122 include time synchronization operations. The digital signal processing module 1122 includes a decoder 1132 for decoding information encoded by the base station prior to transmission. In some embodiments, the decoder 1132 uses redundant information in the encoded signal to recover information lost due to the simultaneous transmission of beacons on the same tones used for data or non-beacon control signals. In some embodiments, the energy detection/signal-to-noise ratio detection module 1124 is part of the digital signal processing module 1122.

In some embodiments, both a second radio frequency module 1128 and a second receiver chain 1130 are used. The second radio frequency module 1128 is similar or identical to the first radio frequency module 1118 and the second receiver chain 1130 is similar or identical to the first receiver chain 1120. In some embodiments, the second radio frequency module 1128 and/or the second receiver chain 1130 are of relatively simple complexity compared to the first radio frequency module 1118 and the first receiver chain 1120, e.g., in terms of the number of gates and/or the number of operations performed. In embodiments having both first and second receiver chains, the first radio frequency module 1118 is tuned to the carrier of the base station sector access point transmitter to be able to receive and process downlink beacon signals, user data signals and non-beacon control signals, while the second radio frequency module 1128 is tuned to another carrier frequency band within which to receive and process beacon signals but not user data signals by way of band selection controller 1126 control signals. Signaling passed through the second radio frequency module 1128 and the second receiver chain 1130 is passed to an energy detection/signal to noise ratio detection module 1124 for beacon detection and identification, rather than to the digital signal processing module 1122 for OFDM modulation symbol information recovery operations.

The transmitter 1104 is connected to a transmit antenna 1116 through which the wireless terminal can transmit uplink signals including user data and a network access point change request to the base station. The transmitter 1104 includes an encoder 1134 that encodes data/information (e.g., user data) for transmission.

Routines 1136 include a communications routine 1140 and wireless terminal control routines 1142. The communication routine 1140 implements the various communication protocols used by the wireless terminal 1100. The wireless terminal control routines 1142 control the operation of the wireless terminal 1100, including performing the methods of the present invention, using data/information 1138. The wireless terminal control routines 1142 include a signaling routine 1144, a receiver controller module 1146, and a carrier band selection module 1148.

Signaling procedures 1144 include downlink signaling procedures 1150 and uplink signaling procedures 1152. Downlink signaling procedures 1150 control the operations pertaining to the reception, recovery and processing of downlink signals received by receiver 1102. Uplink signaling procedures 1152 control operations pertaining to transmission of uplink signals to a base station sector network access point via transmitter 1104.

Downlink signaling procedures 1150 include a beacon module 1154 and a generic signaling module 1156. The beacon module 1154 controls operations pertaining to recovery, detection and identification of beacon signals. For example, upon detecting that the signal energy level of a received tone exceeds a threshold, the received tone may be identified by the beacon module 1154 as a beacon component tone. Thus, by including operations to compare the frequencies of the beacon constituent tones and store system characteristic information 1178, the beacon module 1154 can identify the beacon signal and obtain beacon source transmitter identification information 1190, e.g., carrier identification information, cell identification information, and/or sector identification information.

The operations controlled by the generic signaling module 1156 relate to recovery, detection, and identification of data/information transmitted on non-beacon downlink signals including modulation symbols, e.g., OFDM modulation symbols, processed by the data signal processing module 1122. The generic signaling module 1156 includes a user data module 1158 that controls operations including recovery of user data, including voice, text and video data/information from the peer wireless terminal 1100. The generic signaling module 1156 also includes a non-beacon control operations module 1160 that performs operations to control non-beacon downlink control signals including, for example, pilot signals, timing control signals, power control signals, identifiers and segment assignments, recovery and processing of acknowledgements.

The carrier band selection module 1148 selects a carrier for tuning the first radio frequency module 1118, and in some embodiments the optional second radio frequency module 1128. The carrier band selection module 1146 performs band selection using the detected beacon information 1166, e.g., selecting an access point and/or selecting a changed access point and initiating a handoff. For example, carrier band selection module 1126 may select the carrier to set first radio frequency module 1118 to for ordinary signaling corresponding to the strongest received beacon signal. In an embodiment, using the second rf module 1128, the carrier band selection module 1148 may choose to place the second rf module on different other potential carriers at different times to search for additional beacons for estimation.

The selection signal output from the carrier band selection module 1148 is input to the reception control module 1146, and the reception control module 1146 notifies the band selection controller 1126 in the receiver 1102 of the execution of the selection decision.

Data/information 1138 includes user data 1162, user/device/session/resource information 1164, detection beacon information 1166, carrier frequency information 1168, cell/sector information 1170, downlink user data signals 1172, downlink non-beacon control signals 1174, uplink signals 1176, and system characteristics information 1178.

User data 1162 includes voice, text, and/or video data information to/from a peer wireless terminal in a communication session with wireless terminal 1100. User/device/session/resource information 1164 includes information identifying user/other wireless terminals (e.g., peer wireless terminals in a communication session with wireless terminal 1100), routing information, base station identifiers assigned to wireless terminal 1100, segments assigned to wireless terminal 1100, e.g., uplink and downlink traffic channel segments.

Detection beacon information 1166 includes multiple sets of detection beacon information (beacon 1 information 1180, beacon N information 1182), each set corresponding to a detected beacon signal. Beacon 1 information 1180 includes signal energy information 1184, e.g., energy levels of tones of the detected beacon signal, SNR (signal-to-noise ratio) information 1186 of the detected beacon signal, tone information 1188, e.g., identifying tones of the detected beacon signal, each tone including a corresponding energy level in information 1184. Beacon 1 information 1180 also includes transmitter information 1190, e.g., an identified tone, an identified cell, an identified sector, which has been determined to be associated with the source transmitter of the beacon signal. In some embodiments, multiple different beacon signals, e.g., a list of beacon signals from the same base station sector transmitter, are received to determine transmitter information 1190.

Carrier frequency information 1168 includes information identifying the current access point downlink carrier (e.g., the carrier to which the first radio frequency module 1118 is tuned). Carrier frequency information 1168 also includes information identifying the carrier frequency (the frequency to which transmitter 1104 is tuned) for uplink signaling.

Cell/sector information 1170 includes information identifying the current base station cell and/or sector access point, e.g., a cell identifier such as a slope value in a pilot carrier sequence and a sector identifier identifying the sector type. Downlink user data signals 1172 include information from received signals that include OFDM modulation symbols communicated to wireless terminal 1100 over downlink traffic channel segments. Downlink non-beacon control signal 1174 comprises information in a received signal including OFDM modulation symbols communicated to wireless terminal 1100 over a downlink control channel segment, e.g., an allocation segment, an acknowledgement segment, a power control segment, a time control segment, and/or a pilot segment communicated to wireless terminal 1100. Uplink signal 1176 includes information communicated to the base station sector access point on an uplink channel segment. Uplink signals 1176 include user data communicated upon uplink traffic channel segments. Uplink signal 1176 also includes a handover request message 1192 to initiate a handover request, e.g., in response to a comparison of detected beacon signals. Uplink signals 1176 also include access signals transmitted to establish a new wireless link with a base station sector access point, e.g., base station sector access point selected based on receiving and comparing beacon signals.

System characteristic information 1178 includes multiple sets of base station access point information (base station access point 1 information 1194, base station access point N information 1196) corresponding to different potential access points in the system, e.g., in terms of cells, sectors, and/or tone frequencies. System characteristic information 1178 may be used by beacon module 1154 to evaluate received beacon information, e.g., to determine tone information 1188 of transmitter information 1190. Base station access point 1 information 1194 includes beacon information 1198, time structure information 1199, tone (tone) information 1195, and carrier (carrier) information 1197. Beacon information 1198 includes information identifying the beacon transmitted by the base station access point 1 transmitter, e.g., the set of tones used for the beacon signal, the transmit power level of the beacon tones, the beacon signal type, the location of the beacon tones within the frequency band relative to the lowest tone of the frequency band or relative to the carrier frequency, and/or the tone hopping used for the beacon signal. Time structure information 1199 includes time information and/or timing relationships for base station access point 1, e.g., OFDM symbol timing, slot timing, superslot timing, beacon slot timing, ultraslot timing, and/or timing relationships to other base station access points, e.g., within the same cell. Carrier information 1197 includes carrier identification information identifying the carrier used for uplink, downlink signaling, and associated bandwidth. Tone information 1195 includes information identifying the set of tones associated with the downlink and used to transmit the downlink signal, as well as any structural information relating a particular tone to a particular downlink segment at a particular time in the time series. Tone information 1195 also includes information related to the uplink and used to transmit the set of tones of the uplink signal, as well as any structural information that relates a particular tone to a particular uplink segment at a particular time in the time series.

Fig. 12 is a flow chart 1200 depicting an exemplary method of operating a base station transmitter in a frequency division multiple access communication system, such as an OFDM system, in accordance with the present invention. The transmitter may be an OFDM signal transmitter, such as in a base station, a sector transmitter, which may correspond to a carrier frequency in a sector of a cell using multi-carrier frequencies. The operation starts at step 1202 where the base station is powered on, initialized, and proceeds to step 1204. In step 1204, the base station transmitter transmits a first signal, e.g., a sector of a cell, to a first region, using a set of N tones to communicate information with the first signal in the first region for a first time period that is at least 2 seconds long and N is greater than 20.

Step 1204 includes sub-step 1206, and in some embodiments optional step 1208. Step 1206 is performed every second time period, and in some embodiments optional step 1208 is performed in parallel. In some embodiments, the second time period is repeated periodically within the first time period. In step 1206, the base station transmits a second signal into the first region for a second time period, wherein X is less than 5, and wherein less than 80% of a maximum average total base station power used by the base station transmitter to transmit signals into the first region during any 1 second is allocated to the set of X tones, and wherein each of the X tones is divided by at least 20 times the average power per tone allocated to the plurality of tones during any one second. In some OFDM embodiments, the second time period is a time period for transmitting an orthogonal frequency division multiplexing symbol. In some embodiments, the second time period occurs within the first time period and X sets of tones are a subset of N sets of tones. In various embodiments, user data comprising at least one of voice, text and image data is transmitted on at least one of the N tones transmitted during the first time period, and transmitter information comprising at least one of sector, cell and carrier frequency information is transmitted on at least one of the X tones during the second time period. In some embodiments X is equal to 1 or 2. In some embodiments, such as embodiments without step 1208, none of the N-X tones belonging to the set of N tones but not the set of X tones are used during the second time period. In some implementations, at least half of the N-X tones belonging to the set of N tones but not the set of X tones are unused in the first region during the second time period. In various embodiments, a plurality of N-X tones belonging to the set of N tones are used within the first region during the second time period.

In step 1208, during the second time period, the base station transmits user data using Y tones, the Y tones belonging to the set of N tones, where Y is a positive integer greater than 1, and more than 20% of the total transmitter power used to transmit signals to the first region during the second time period is allocated to the Y tones during the second time period. In some embodiments, more than 50% of the total transmit power used to transmit signals to the first region during the second time period is allocated to the Y tones during said second time period. In some embodiments, the Y tones include at least 70 tones. In various embodiments, transmitting user data includes transmitting modulation symbols on the Y tones, each of the Y tones conveying a symbol.

Fig. 13 is a flow chart 1300 of another exemplary method of operating a base station transmitter in a frequency division multiplexed system in accordance with the present invention. Operation begins at step 1302 where the base station powers up, initializes, and proceeds to step 1304.

In step 1304, the base station transmitter transmits a first signal into a first region, and conveys information using a set of N tones within the first region with the first signal for a first time period, the first time period being at least 2 seconds long, where N is greater than 20. Step 1304 includes sub-steps 1306, 1308, and 1310. In sub-step 1306, for each second time period, the base station transmitter transmits a second signal into the first region for a second time period, the second signal comprising a set of X tones, wherein X is less than 5, and wherein 80% or less of a maximum average total base station transmit power used by the base station transmitter to transmit signals into the first region during any 1 second within the first time period is allocated to the set of X tones, and wherein each of the X tones is allocated at least 20 times the average power per tone allocated to the plurality of tones during any 1 second within the first time period. In sub-step 1308, for each third time period, the base station transmitter transmits a third signal in the first region for a third time period, the third signal comprising a set of Y tones, where Y ≦ N, each tone in the third set of Y tones allocated a power of at most 8 times an average per tone power allocated to the plurality of tones in the first time period, the third time period having the same duration as the second time period. In sub-step 1310, for each fourth time period, the base station transmits a fourth signal comprising G tones in the first region for a fourth time period, wherein G is less than 5, and wherein the base station transmitter allocates less than 80% of the maximum average total base station transmit power used to transmit signals in the first region during any 1 second in the first time period to the G tones, and each of the G tones has allocated at least 20 times the power per tone allocated to the plurality of tones in any 1 second period.

In some embodiments, the third time period and the second time period overlap, whereupon the method further comprises: modulating at least two of data, control, and pilot signals on at least some tones of the set of Y tones. In some embodiments, the third segment and the second segment do not intersect, and the method further comprises: modulating at least two of data, control, and pilot signals on at least some tones of the set of Y tones. In various embodiments, at least one of the X tones is transmitted at a predetermined fixed frequency, and at least one of the X tones is transmitted using a frequency that is a fixed offset from the lowest frequency tone of the set of N tones, the fixed offset ≧ 0. In some embodiments, at least one of the X tones is transmitted on a transmit frequency that depends on at least one of a base station identifier and a sector identifier.

In some embodiments, the second time period is repeated every time within the first time period, and the third time period is repeated at least Z times within the first time period, wherein Z is at least 10. In various embodiments, Z is at least 400.

In some embodiments, a frequency of at least one of the G tones is dependent on at least one of a base station identifier and a sector identifier, and the at least one of the G tones does not belong to the set of X tones. For example, at least one of the X tones corresponds to a carrier beacon signal and at least one of the G tones corresponds to a cell/sector beacon, and there is no overlap of the second and fourth time periods. In some embodiments, the second and fourth time periods repeat at different rates.

Fig. 14 is a flow chart 1400 of an exemplary method of operating a base station transmitter in a communication system in accordance with the present invention. In some embodiments, the base station transmitter is a sector transmitter of a base station. In various embodiments, the sector transmitter corresponds to a single carrier frequency of a plurality of carrier frequencies used by the base station sector. Operation begins at step 1402 where the base station is powered on and initialized. Operation proceeds from step 1402 to step 1404.

In step 1404, the base station transmitter transmits a signal during a first time period, the signal comprising a plurality of tones, each tone corresponding to a different frequency, the signal comprising a beacon and a user data signal, the beacon being transmitted on at least one tone, the user data signal being transmitted in parallel with the beacon on tones not used to transmit the beacon, the first transmitter transmitting user data with an average per tone power less than 1/20 of the per tone transmit power used to transmit the beacon.

Step 1404 includes substep 1406. In sub-step 1406, the base station transmitter transmits information indicative of at least one of a cell identifier, a sector identifier and a carrier identifier using the frequency of a tone within said transmitted beacon signal. Operation proceeds from step 1404 to step 1408.

In some embodiments, the step of transmitting the signal for the first time period comprises: user data is transmitted on at least 100 tones, and the beacon is transmitted on at least 3 tones. In some embodiments, at least N times the average energy per signal tone of said transmitted signal is transmitted on the respective tones within said signal used to transmit said beacon signal, where N is a positive value greater than 5, 20, 99 or 150.

In various embodiments, the beacon signal is transmitted to a frequency band used by base stations adjacent to the cell in which the base station transmitter is located, but which is not used by the base station transmitter to transmit user data.

In step 1408, the base station transmitter transmits a signal during a second time period, the signal including user data but not including any tones having a per tone transmission power greater than 1/10 used to transmit the beacon signal.

In one particular example method of operating a base station transmitter in a frequency division multiplexed communication system in accordance with this invention, the method comprises the steps of: transmitting a first signal to a first region, e.g., a sector, to communicate information using a set of N tones for a first time period that is at least two seconds long, where N is greater than 10; transmitting a second signal comprising a set of X tones to the first region for a second time period, wherein X is less than 5, and wherein the base station transmitter is allocated to the set of X tones (sometimes X is 1 or 2) for less than 80% of the maximum average total base station transmit power used to transmit signals to the first region for any one 1 second period in the first time period, and each of the X tones allocated power receives at least 20 times (sometimes 40, 60 or more times) the average power per tone allocated to the plurality of tones for the any one second period. In some embodiments, the first region is a sector of a cell; and the communication system is an orthogonal frequency division multiplexing system, and wherein the second time period is a time period for transmitting an orthogonal frequency division multiplexing symbol. The particular example method includes: transmitting a third signal (e.g., a non-beacon signal) in the first region for a third time period, the third signal not including the second signal, the third signal including a set of Y tones, wherein Y ≦ N, each tone of the third set of Y tones allocated a power at most 8 times an average per tone power allocated to the plurality of tones in the first time period. The method sometimes further comprises: modulating at least data, control, and pilot signals on the Y sets of tones. Different information is modulated onto different tones, e.g., data information is modulated onto one or more tones, control and tone information is modulated onto respective different tones. In some implementations, at least one of the X tones is transmitted on a transmit frequency that depends on at least one of a base station identifier and a sector identifier. In some implementations, the second time period is repeated once every time within the first time period, and the third time period is repeated at least Z times within the first time period, where Z is at least 10, and in some instances Z is at least 20, 40, or 400. Thus, in a two second time interval, the method includes several beacon periods, but no beacon signal is transmitted in more periods, e.g., sometimes each beacon signal period corresponds to more than 400 user data periods. Each of the second and third time periods includes one or more OFDM symbol transmission time periods. The duration of the second and third time periods may be the same or different, depending on the implementation. In particular, the user data tone is typically transmitted at 1/8 times the average beacon tone transmission power, and in some cases, the beacon tone transmission power is much higher than the user data tone transmission power, e.g., 20 times or more. The above description is only a few exemplary implementations and is not the only possible implementation in accordance with the present invention.

In an exemplary embodiment, a base station transmitter for use in a communication system, comprising: a transmitter for transmitting a signal comprising a plurality of tones, each tone corresponding to a different frequency; a transmitter control module that controls the transmitter to transmit a signal using a plurality of signal tones transmitted in parallel during a single symbol transmission time period, each signal tone corresponding to a different frequency, the control module transmitting user data on the plurality of signal tones by devoting greater than 20% of a maximum possible transmit power of the base station transmitter during a symbol time period to the tones used to transmit user data, wherein the signal further includes a beacon signal transmitted on at least one tone where user data is not transmitted, the beacon signal being transmitted with a power greater than 20 times a transmit power of any signal tone used to transmit user data. In some implementations, the transmitter control module controls the transmitter to transmit beacon signals within a frequency band used by neighboring base stations to transmit user data but not used by the base station transmitter to transmit user data, e.g., the frequency band to which the beacon signals are transmitted is typically used by neighboring sectors or base station transmitters to establish a communication link with a wireless terminal served by the transmitter. In some examples, the second time period occurs within the first time period; the X tones are a subset of the N tones. In an exemplary base station embodiment, the base station includes stored user data including at least one of transmitted voice, text and image data; and said first control module comprises control logic that controls a transmitter to transmit user data on at least one tone during said first time period and to transmit user data on a plurality of Y tones (a subset of said N tones), said Y tones not being included in said X tones during said second time period.

In another exemplary base station embodiment, the base station transmitter of the present invention is used in a communication system, e.g., an OFDM communication system, comprising: a transmitter for transmitting a signal comprising a plurality of tones, each tone corresponding to a different frequency; a transmitter control module that controls the transmitter to transmit a signal using a plurality of signal tones transmitted in parallel during a single symbol transmission time period, each signal tone corresponding to a different frequency, the control module transmitting user data on the plurality of signal tones by devoting greater than 20% of a maximum possible transmit power of the base station transmitter during a symbol time period to the tones used to transmit user data, wherein the signal further includes a beacon signal transmitted on at least one tone where user data is not transmitted, the beacon signal being transmitted with a power greater than 20 times a transmit power of any signal tone used to transmit user data. The base station transmitter control module includes control logic that controls the transmitter to transmit the beacon signal within a frequency band used by neighboring base stations to transmit user data, but not used by the base station transmitter to transmit user data. The transmitter may be a sector transmitter, in which case the first region is a sector of a cell, in some embodiments the communication system is an orthogonal frequency division multiplexing system, and the second time period is a time period for transmitting orthogonal frequency division multiplexing signals. In some base station implementations, at least one of the X tones is transmitted on a frequency that depends on at least one of a base station identifier and a sector identifier. The base station includes control circuitry and/or logic for transmitting a third signal, e.g., a user data signal, to the first region during a third time period, the third signal not including the second data signal, which may be a beacon signal, the third signal including a set of Y tones, where Y ≦ X, each tone of the third set of Y tones allocated a power of at most 8 times an average per tone power allocated to the plurality of tones during the first time period. Thus, in such an implementation, signals corresponding to user data will be transmitted with little power, e.g., 1/20 or less of the power allocated to the beacon tones. The base station includes a control module and/or logic for transmitting a third signal to the first region for a third time period, the third signal not including the second signal, the third signal including a set of Y tones, wherein Y ≦ N, each tone of the third set of Y tones allocated at most 8 times an average per tone power allocated to the plurality of tones for the first time period, the third time period having a same duration as the second time period, wherein the second time period repeats every time in the first time period, and the third time period repeats at least Z times in the first time period, wherein Z is at least 10, and in some embodiments, Z is at least 400.

Although described primarily with respect to OFDM systems, the methods and apparatus of the present invention are applicable to a wide range of communication systems, including: many non-OFDM and/or non-cellular systems.

A control module, e.g., a transmission control module, implemented in accordance with the present invention may perform a variety of transmission control operations. In such a case, the module includes circuitry and/or logic, e.g., stored instructions, to perform each control operation belonging to the control module. Thus, the signal control module may employ a variety of means, one of which performs each control operation belonging to the control module. Also, a routine may include instructions to perform various operations, where an instruction corresponding to a particular operation represents one means to perform the operation.

The nodes described in the various embodiments of the present application are implemented using one or more modules for performing the steps corresponding to one or more methods of the present invention, e.g., carrier band selection, digital signal processing, energy detection/signal-to-noise ratio detection, decoding, time synchronization, signal quality detection, etc. In some embodiments, various features of the present invention are implemented using modules. These modules are implemented in software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions (e.g., software embodied in a machine readable medium such as a memory device including RAM, floppy disk, etc.) to control a machine (e.g., general purpose computer with or without additional hardware) to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, the present invention also relates to a machine-readable medium comprising executable instructions to run a machine (e.g., a processor and associated hardware) to perform one or more of the steps of the above-described method(s).

Various other modifications to the methods and apparatus of the present invention will be apparent to those skilled in the art in view of the above description. Such modifications still fall within the scope of the present invention. The methods and apparatus of the present invention may be, and in some embodiments are, used in conjunction with CDMA, Orthogonal Frequency Division Multiplexing (OFDM), and/or various other types of communications techniques to provide wireless communications links between access nodes and mobile nodes. In some embodiments the access nodes are implemented using base stations which establish communications links with mobile nodes using OFDM and/or CDMA techniques. In various embodiments the mobile nodes may be notebook computers, Personal Digital Assistants (PDAs), or other portable devices including transmitter/receiver circuits, logic and/or routines, for implementing the methods of the present invention.

Claims (61)

1. A method for operating a base station transmitter in a frequency division multiplexed communication system, the method comprising:

transmitting a first signal into a first region using a set of N tones during a first time period to convey information, the first time period being at least 2 seconds long, where N is greater than 10; and

transmitting a second signal into said first region for a second time period, said second signal comprising a set of X tones, wherein X is less than 5, and wherein said base station transmitter allocates less than 80% of a maximum average total base station transmit power used to transmit signals into said first region during any 1 second within said first time period to said set of X tones, and wherein each of said X tones allocated power receives at least 20 times the average power per tone allocated to the plurality of tones during said any one second.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of a red light source, a green light source, and a blue light source,

wherein the second time period occurs within the first time period; and

wherein the X tones are a subset of the N tones.

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of a red light source, a green light source, and a blue light source,

wherein user data comprising at least one of voice, text and image data is transmitted on at least one of the N tones transmitted during the first time period; and

wherein transmitter information including at least one of sector, cell, and carrier frequency information is transmitted on at least one of the X tones during the second time period.

4. The method of claim 1, further comprising:

transmitting user data using Y tones in the second time period, the Y tones belonging to the set of N tones but not included in the X tones, wherein Y is a positive integer greater than 1, more than 20% of a total transmitter power used in the second time period being allocated to the Y tones in the second time period.

5. The method of claim 4, wherein more than 50% of a total transmitter power used in the second time period is allocated to Y tones in the second time period.

6. The method of claim 4, wherein the Y tones comprise at least 70 tones.

7. The method of claim 4, wherein transmitting user data comprises:

transmitting modulated symbols on the Y tones, each of the Y tones conveying a symbol.

8. The method of claim 7, wherein the transmitter is an OFDM signal transmitter.

9. The method of claim 7, wherein the transmitter is a sector transmitter within a base station.

10. The method of claim 7, wherein the transmitter is a sector transmitter corresponding to a carrier frequency within a sector of a cell using multi-carrier frequencies.

11. The method of claim 1, wherein the first area is a sector of a cell.

12. The method of claim 1, wherein X equals one or two.

13. The method of claim 1, wherein at least half of the N-X tones belonging to the set of N tones but not the set of X tones are unused in the first region during the second time period.

14. The method of claim 13, wherein none of the N-X tones belonging to the set of N tones but not the set of X tones are used within the first region during the second time period.

15. The method of claim 13, wherein, during the second time period, a plurality of N-X tones belonging to the set of N tones but not to the set of X tones are used within the first region.

16. The method of claim 1, wherein the first and second light sources are selected from the group consisting of a red light source, a green light source, and a blue light source,

wherein the first area is a sector of a cell; and is

Wherein the communication system is an orthogonal frequency division multiplexing system, and

wherein the second time period is a time period for transmitting an orthogonal frequency division multiplexing symbol.

17. The method of claim 16, wherein the second time period is repeated periodically within the first time period.

18. The method of claim 16, wherein the method further comprises:

transmitting a third signal into the first region for a third time period, the third signal excluding the second signal, the third signal comprising a set of Y tones, wherein Y ≦ N, each tone of the third set of Y tones allocated a power of at most 8 times an average per tone power allocated to the plurality of tones in the first time period.

19. The method of claim 18, wherein the third time period and the second time period overlap, the method further comprising:

modulating at least two of data, control, and pilot signals on at least some tones of the set of Y tones.

20. The method of claim 18, wherein the third time period and the second time period are disjoint, the method further comprising:

modulating at least two of data, control, and pilot signals on at least some tones of the set of Y tones.

21. The method of claim 16, wherein the step of selecting the target,

wherein at least one of the X tones is transmitted on a predetermined fixed frequency; and is

Wherein the at least one of the X tones is transmitted using a frequency that is a fixed offset from the lowest frequency tone in the set of N tones, the fixed offset being ≧ 0.

22. The method of claim 16, wherein the step of selecting the target,

wherein at least one of the X tones is transmitted on a transmit frequency determined based on at least one of a base station identifier and a sector identifier.

23. The method of claim 18, wherein the second time period repeats every time within the first time period, and the third time period repeats at least Z times within the first time period, wherein Z is at least 10.

24. The method of claim 23, wherein Z is at least 400.

25. The method of claim 16, further comprising:

transmitting a fourth signal comprising G tones into said first region for a fourth time period, wherein G is less than 5, and wherein said base station transmitter allocates less than 80% of said maximum average total base station transmitter power used to transmit into said first region during any 1 second of said first time period to said G tones, and each of said G tones allocated power is allocated at least 20 times the power per tone allocated to the plurality of tones in said any 1 second period.

26. The method of claim 25, wherein the step of,

wherein a frequency of at least one of the G tones is dependent on at least one of a base station identifier and a sector identifier, and

wherein the at least one of the G tones does not belong to the set of X tones.

27. The method of claim 26, wherein the second and fourth time periods repeat periodically during the first time period.

28. A base station for use in a frequency division multiplexed communication system, the base station comprising:

a transmitter to transmit information into a first region using a set of N tones, where N is greater than 10;

a first control module connected to the transmitter for controlling the transmitter to transmit a first signal to a first area for a first time period, the first time period being at least 2 seconds long; and

a second control module coupled to the transmitter for controlling the transmitter to transmit a second signal in a second time period into the first region, the second signal comprising a set of X tones, wherein X is a positive integer less than 5, and wherein less than 80% of a maximum average total base station transmit power used by the base station transmitter to transmit into the first region during any 1 second in the first time period is allocated to the set of X tones, and wherein each of the X tones is allocated at least 20 times the maximum average power per tone allocated to the plurality of tones during any 1 second in the first time period.

29. The base station of claim 28, wherein the base station,

wherein the second time period occurs within the first time period; and is

Wherein the X tones are a subset of the N tones.

30. The base station of claim 29, further comprising:

stored user data comprising at least one of voice, text and image data to be transmitted; and

wherein the first control module controls the transmitter to transmit user data on at least one tone and to transmit user data on Y tones in the first time period, the Y tones being a subset of the N tones, the Y tones not included in the X tones in the second time period.

31. The base station of claim 29, wherein said control module allocates more than 20% of a total transmitter power used in said second time period to Y tones in said second time period.

32. The base station of claim 31, wherein said control module allocates more than 50% of a total transmitter power used in said second time period to Y tones in said second time period.

33. The base station of claim 32, wherein Y is greater than 50.

34. A method for operating a base station transmitter in a communication system, the method comprising:

transmitting a signal in a first time period, said signal comprising M signal tones, where M is greater than 10, each signal tone corresponding to a different frequency, said first time period being at least two seconds long, said signal comprising a beacon signal and a user data signal, said beacon signal being transmitted on at least one tone, and said user data signal being transmitted in parallel with said beacon signal on a tone not used to transmit said beacon signal, said user data being transmitted by said first transmitter with more than 20% of a maximum average total base station transmit power with which said first base station transmitter transmits signals into a first area in any 1 second time period of said first time period.

35. The method of claim 34, wherein at least N times the average energy per signal tone of said transmitted signal is transmitted on each of the individual tones within said signal used to transmit said beacon signal, where M is a positive value greater than 5.

36. The method of claim 34, wherein at least N times the average energy per signal tone of the transmitted signal is transmitted on each of the individual tones within the signal used to transmit the beacon signal, where N is a positive value greater than 20.

37. The method of claim 34, wherein at least N times the average energy per signal tone of the transmitted signal is transmitted on each of the individual tones within the signal used to transmit the beacon signal, where N is a positive value greater than 99.

38. The method of claim 37, wherein at least N times the average energy per signal tone of said transmitted signal is transmitted on each of the individual tones within said signal used to transmit said beacon signal, where N is a positive value greater than 150.

39. The method of claim 35, further comprising:

transmitting information indicative of at least one of a cell identifier, a sector identifier and a carrier identifier using a frequency of a tone within said transmitted beacon signal.

40. The method of claim 39, wherein the beacon signal is transmitted into a frequency band used by base stations adjacent to a cell in which the base station transmitter is located, but which is not used by the base station transmitter to transmit user data.

41. The method of claim 40, wherein the step of transmitting signals during the first time period comprises:

transmitting user data on at least 100 tones, an

Transmitting the beacon signal on less than 3 tones.

42. The method of claim 41, further comprising:

transmitting a signal during a second time period, the signal including user data but not including any tones having a per tone transmit power greater than 1/10 of the transmit power used to transmit each tone of the beacon signal.

43. The method of claim 34, wherein the base station transmitter is a sector transmitter of a base station.

44. The method of claim 43, wherein the base station transmitter is a sector transmitter corresponding to a single carrier frequency of a plurality of carrier frequencies used by a base station sector.

45. A base station transmitter for use in a communication system, the transmitter comprising:

a transmitter for transmitting a signal comprising a plurality of tones, each tone corresponding to a different frequency; and

a transmitter control module that controls the transmitter to transmit a signal using a plurality of signal tones transmitted in parallel, each signal tone corresponding to a different frequency, in a single symbol transmission time period, the control module transmitting user data on the plurality of signal tones by devoting greater than 20% of a maximum possible transmit power of the base station transmitter to the tones used to transmit user data during a symbol time period, wherein the signal further includes a beacon signal transmitted on at least one tone where user data is not transmitted, the beacon signal being transmitted with more than 20 times the transmit power of any signal tone used to transmit user data.

46. The method of claim 45, wherein said transmitter control module controls said transmitter to transmit said beacon signal in a frequency band used by an adjacent transmitter to transmit user data, but which frequency band is not used by said transmitter to transmit user data.

47. The base station of claim 28, wherein the base station,

wherein the first area is a sector of a cell; and is

Wherein the communication system is an orthogonal frequency division multiplexing system, and

wherein the second time period is a time period for transmitting an orthogonal frequency division multiplexing symbol.

48. The base station of claim 28, wherein at least one of the X tones is transmitted on a frequency determined based on at least one of a base station identifier and a sector identifier.

49. The base station of claim 28, further comprising:

a control module configured to transmit a third signal to the first region in a third time period, the third signal excluding the second signal, the third signal including a set of Y tones, wherein Y ≦ N, and a power allocated to each tone of the third set of Y tones is at most 8 times an average power per tone allocated to the plurality of tones in the first time period.

50. The base station of claim 28, further comprising:

a control module for transmitting a third signal in a third time period to the first region, the third signal excluding the second signal, the third signal comprising a set of Y tones, wherein Y ≦ N, each tone of the third set of Y tones having allocated power up to 8 times the average power per tone allocated to the plurality of tones in the first time period, the third time period having the same duration as the second time period;

wherein for each repetition of the second time period within the first time period, the third time period is repeated at least Z times within the first time period, wherein Z is at least 10.

51. The base station of claim 50, wherein Z is at least 400.

52. The method of claim 34, wherein the step of selecting the target,

wherein the first area is a sector of a cell; and is

Wherein the communication system is an orthogonal frequency division multiplexing system, and

wherein the beacon signal is transmitted during a second time period, and

wherein the second time period is within the first time period, the second time period being a time period for transmitting an orthogonal frequency division multiplexing symbol.

53. The method of claim 34, wherein at least one tone of the beacon signal is transmitted on a frequency determined from at least one of a base station identifier and a sector identifier.

54. The method of claim 52, wherein the method further comprises:

transmitting a third signal into the first region for a third time period, the third signal excluding the second signal, the third signal comprising a set of Y tones, where Y ≦ M, each tone of the third set of Y tones allocated power being up to 8 times the average per tone power allocated to the plurality of tones in the first time period.

55. The method of claim 52, wherein the method further comprises:

transmitting a third signal into the first region for a third time period, the third signal excluding the second signal, the third signal comprising a set of Y tones, where Y ≦ M, each tone of the third set of Y tones allocated power up to 8 times the average power per tone allocated to the plurality of tones in the first time period, the third time period having the same duration as the second time period;

wherein for each repetition of the second time period within the first time period, the third time period is repeated at least Z times within the first time period, wherein Z is at least 10.

56. The method of claim 55, wherein Z is at least 400.

57. The base station of claim 45, wherein the base station is further configured to,

wherein the base station transmitter transmits to a first area within a first time period, the first area being a sector of a cell; and

wherein the communication system is an orthogonal frequency division multiplexing system, and

wherein the beacon signal is transmitted within a second time period of the first time period, the second time period being a time period for transmitting an orthogonal frequency division multiplexing symbol.

58. The base station of claim 45, wherein at least one tone included in the beacon signal is transmitted on a frequency determined based on at least one of a base station identifier and a sector identifier.

59. The base station of claim 57, further comprising:

a control module to transmit a third signal in the first region for a third time period, the third signal not including the second signal, the third signal including a set of Y tones, wherein Y ≦ N, where N is the set of tones used by the base station transmitter for downlink signaling, each tone of the third set of Y tones allocated power allocated at a power up to 8 times an average per tone power allocated to the plurality of tones in the first time period.

60. The base station of claim 57, further comprising:

a control module for transmitting a third signal in the first region for a third time period, the third signal not including the second signal, the third signal including a set of Y tones, wherein Y ≦ N, where N is the set of tones used by the base station transmitter for downlink signaling, each tone in the third set of Y tones allocated power allocated at most 8 times the average per tone power allocated to the plurality of tones in the first time period, the third time period and the second time period having the same duration; and

wherein for each repetition of the second time period within the first time period, the third time period is repeated at least Z times within the first time period, wherein Z is at least 10.

61. The base station of claim 60, wherein Z is at least 400.