CN1305669A - Signal decoding with or without second synchronization word in mobile communication system - Google Patents

Abstract

A time division multiple access (TDMA) radio communication system (100) accommodates signal decoding by a mobile station (130) with and without a second synchronization word (214). The radio communication system includes at least one base station (102, 104) to transmit radio signals during a succession of time slots (202, 204, 206) including a current time slot (202) and a subsequent time slot (204). The radio signals include an indication of whether transmission of the subsequent time slot is guaranteed. The system further includes at least one mobile station to receive the radio signals in accordance with the indication.

Description

Decoding of signals with or without a second sync word in mobile communication systems

related applications

This non-provisional application claims priority to provisional application 60/085,710, filed May 15, 1998, and is claimed by Paul W. Dent and Krister Raith.

Background of the invention

The present invention generally relates to transmitting and receiving signals in a mobile radio communication system. In particular, the invention relates to decoding signals in a mobile radio communication system, suspending transmission from a base station of the system for a selected period of time.

In a Time Division Multiple Access (TDMA) wireless communication system, each transmitter in the system is assigned or allocated a time slot for transmitting wireless signals. All other transmitters are silent during the time slot so that the designated receiver can clearly receive the radio signal. If the radio communication system is a two-way mobile system, such as a cellular radiotelephone system, the radio carrier frequency in the first frequency band is divided into time slots for communication from the base station to a plurality of mobile stations, while the radio carrier frequencies in the second frequency band The radio carrier frequency is divided into time slots for communication from different ones of the plurality of mobile stations to the base station. A base station communicates with mobile stations within a fixed geographic area close to the base station, and other adjacent base stations serve mobile stations in adjacent areas.

During certain time slots, the base station transmits control and timing information. Such information includes, for example, the identity of the mobile station to which a call is received on a communication channel, and synchronization and timing information on a synchronization or Sync channel. Mobile stations in the system receive the synchronization channel and use the information in the synchronization channel to synchronize their timing with the timing of the base stations. Typically, each time slot also includes known data patterns that allow the mobile station to estimate the phase and amplitude of the channel, which is useful for decoding the symbols transmitted in the time slot.

It is known to improve the reception and decoding of symbols by using a synchronization word at the beginning of the current slot and a synchronization (Sync) word at the beginning of the next slot and the end of the current slot. The current or first sync word may not be received reliably because of fading or other disturbances on the channel. By storing received signal samples comprising the second synchronization word, the stored signal samples can be decoded using the first or second synchronization word or both. This technique is described in US Patent 5,335,250, issued August 2, 1994 to Dent et al., and US Patent 5,841,816, issued November 24, 1998 to Dent et al. These two patents are commonly assigned to the applicant of the present invention with the present application and are incorporated herein by reference. Certain mobile stations are currently in use which rely on receiving the second sync word for optimum performance.

In some mobile radio systems it is proposed to suspend or alter the transmission of information including synchronization words when slots are not allocated. If the time slot is not allocated, no mobile station is currently using the time slot. This may cause the phase, amplitude or direction transmitted by the base station to change in subsequent time slots relative to the current time slot, which may degrade the performance of existing mobile stations without utilizing the present invention. However, transmission of information by base stations in unassigned time slots is desirably avoided in order to reduce interference to receivers in the surrounding area. Eliminating the transmission of sync words and other information during unassigned time slots will reduce or eliminate such co-channel interference, improving overall performance in the radio system. This improvement is threatened by reduced quality due to the removal of the mobile station's ability to utilize the second sync word.

For mobile stations that rely on receipt of a second synchronization word to improve communications, the synchronization word is eliminated if the unassigned time slot allows time slots to be allocated to the mobile station or in terms of characteristics such as the timing, phase, or direction of transmissions in the unassigned time slot changes will cause problems. The mobile station may not successfully decode the channel, or may spend too much time searching for the second sync word. Therefore, there is a need for a method and apparatus for providing the elimination of certain time slots transmitted by base stations in a mobile radio communication system without degrading the performance of the remaining time slots.

Brief description of the drawings

Fig. 1 is a block diagram of a wireless communication system;

FIG. 2 is a diagram illustrating a communication format in the wireless communication system of FIG. 1;

FIG. 3 is a flowchart illustrating a method for operating a base station in the radio communication system of FIG. 1;

4 is a flowchart illustrating a method for operating a first type of mobile station in the wireless communication system of FIG. 1; and

FIG. 5 is a flowchart illustrating a method for operating a second type of mobile station in the wireless communication system of FIG. 1. FIG.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT

Referring now to the drawings, FIG. 1 illustrates a wireless communication system 100 comprising at least one base station 102,104 and at least one mobile station 130. Wireless communication system 100 may be any two-way wireless communication system, such as a cellular radiotelephone system, a personal communication system (PCS), a mains radio system, or others. In the illustrated embodiment, the wireless communication system 100 is a cellular radiotelephone system operating in accordance with Interim Standard IS-136 promulgated by the Telecommunications Industry Association/Electronic Industries Association (TIA/EIA).

In FIG. 1 , a system 100 is illustrated with two base stations, including a base station 102 and a base station 104 . In general, all base stations are configured similarly, and the structure and operation of the base stations will be described in conjunction with base station 102 . The base stations of the system including base station 102 and base station 104 are linked together to form a network. The network is controlled by a Mobile Switching Center (MSC) 106 . MSC 106 is connected to each base station 102,104 by land line, telephone link or wireless link. MSC 106 controls the operation of the entire network, provides connectivity to the Public Switched Telephone Network (PSTN) and controls the interoperation of base stations to provide functions such as handover of radio communications between two base stations and a single mobile station in system 100 .

Base station 102 is a model for base station structure and operation. Base station 102 includes controller 110 , transmitter 112 , receiver 114 , memory 116 , clock 118 and antenna 120 . The controller 110 controls the overall operation of the base station 102 . Each base station provides two-way radio communication with one or more mobile stations in a fixed geographic area near the base station. Each geographic area may be divided into sectors, with each sector served by an antenna or portion of an antenna 120 .

Transmitter 112 utilizes antenna 120 to transmit radio signals to mobile stations, such as mobile station 130 within a fixed geographic area around base station 102 . Transmitter 112 may include functions such as encoding, insertion and modulation. Receiver 114 converts radio signals received at antenna 120 to digital data for use by base station 102 . Receivers may include functions such as filtering, demodulation and decoding. Memory 116 stores data and instructions for operating controller 110 and for use by other circuits within mobile station 102 .

Clock 118 provides a time base for operating base station 102 . Typically, devices operating in system 100 must be close to synchronization. Including base station, MSC 106 and mobile station. Clock 118 receives synchronization signals from MSC 106 and is used in turn to provide synchronization signals to mobile stations such as mobile station 130 .

Those skilled in the art will appreciate that the base stations 102, 104 may include other functionality and other circuitry as well. These functions include managing call initiation with the mobile station and handover of communications from one base station to another with the mobile station.

Mobile station 130 is an example of a mobile station that may operate in radio communication system 100 . A mobile station may be any radio capable of two-way wireless communication with a remote base station, such as a cellular telephone, PCS telephone or other two-way radio. In the illustrated embodiment, mobile station 130 is a mobile telephone capable of operating in accordance with IS-136. Mobile station 130 in the illustrated embodiment includes antenna 132 , receive path 134 , transmit path 136 , controller 138 , memory 140 , user interface 142 , battery 144 , clock 146 and synthesizer 148 .

Receive path 134 receives wireless signals detected at antenna 132 and generates digital data for use within mobile station 130 . Receive path 134 includes analog front end 150 , demodulator 152 and decoder 154 . Analog front end 150 includes a low noise amplifier and appropriate filters for detecting and filtering radio signals received at antenna 132 . Analog front end 150 may further include circuitry, such as a mixer coupled to synthesizer 148 , for downshifting the frequency of broadcast radio signals to lower frequencies for more convenient processing in mobile station 130 . The demodulator 152 determines an estimate of the multipath propagation channel by processing the received signal samples using a sync word or known symbol pattern, and then processes the signal samples using the channel estimate to produce a soft signal that compensates for multipath and intersymbol interference. decision making. The soft decisions are then passed from demodulator 152 to decoder 154 where error correction encoding is performed to generate error corrected information to controller 138 .

Transmit path 136 converts the digital data generated by controller 138 into radio signals for transmission using antenna 132 . Transmit path 136 includes encoder 160 , modulator 162 and transmitter 164 . Encoder 160 encodes the digital data provided by controller 138 into the format required for communication within system 100 including plug-in. The encoded data is provided to modulator 162, which modulates the carrier signal provided by combiner 148 with the data. The modulated carrier is provided to a transmitter 164, which provides functions such as power amplification and filtering. The amplified carrier wave is then applied to antenna 132 for transmission to remote base stations, such as base stations 102,104.

The controller 138 controls the general functions of the mobile station 130 . Controller 138 is preferably a microcontroller, a digital signal processor, or a combination thereof, and operates in response to data and instructions stored in memory 140 . User interface 142 allows the mobile station to be controlled by the user and typically includes a keypad, microphone, speaker and display. The battery 144 provides operating power for the mobile station 130 . Clock 146 provides timing for the circuits of mobile station 130 . In particular, clock 146 provides timing signals for use by controller 138 so that mobile station 130 including controller 138 may remain synchronized with the rest of communication system 100 .

In the illustrated embodiment, wireless communication system 100 is a time division multiple access (TDMA) wireless communication system. That is, in system 100, each mobile transmitter in the system, when activated, is assigned or assigned a time slot for transmitting wireless signals. All other other mobile transmitters in the same cell using the same frequency are stationary during that time slot. Allows designated receivers to clearly receive radio signals on a channel. Of course, in another cell or another frequency, other mobile stations may independently use the same time slot.

An example of a TDMA radio communication system is a mobile telephone system according to Interim Standard IS-136. IS-136 specifies communication frames with six time slots, however, usually assigned in pairs to form full rate channels. The full-rate channel is therefore actually a three-slot TDMA system. By combining time slots on an uplink frequency with timeslots on a downlink frequency, a duplex channel is established for establishing two-way communication between a base station and a particular mobile station.

Fig. 2 shows a communication format in the wireless communication system of Fig. 1 . FIG. 2 shows a portion of a communication frame 200 including three time slots, a first time slot 202 , a second time slot 204 and a third time slot 206 . Timeslots 202, 204, 206 are all transmitted by base stations in system 100 of FIG. 1 .

Each slot includes a sync word. Thus the first time slot 202 includes the synchronization word 212 , the second time slot 204 includes the synchronization word 214 and the third time slot 206 includes the synchronization word 216 . A synchronization word or Sync word comprises a predetermined data pattern in a predetermined location near the beginning of each time slot. The sync word is used by the receiving mobile station for synchronizing timing and decoding transmitted slots.

Each time slot and its associated synchronization word are specified by the transmitting base station for reception by individual mobile stations adjacent to the base station. However, in the current IS-136 system, all three slots are always transmitted, so the assigned mobile station can receive other slots, such as subsequent slots and better slots than its assigned slot . In IS-136, the transport format exhibits time inverse symmetry so that a mobile station can demodulate its information from the first synchronization word forward or backward from the second synchronization word. However, in future systems, time slots may be omitted when no data is being transmitted. to reduce interference to non-designated receivers, but deprives designated receivers of the second sync word.

It is known to improve the reception and decoding of symbols by a mobile station using the synchronization word of the current time slot and the subsequent time slot. This technique is described in US Patent No. 5,335,250, issued August 2, 1994 to Dent et al., and US Patent No. 5,841,816, issued November 24, 1998 to Dent et al. These two patents are commonly assigned to the applicant of the present invention with the present application and are incorporated herein by reference. These incorporated reference decoding techniques, or other suitable decoding techniques, are referred to herein as first decoding algorithms or techniques. According to the presently disclosed embodiment, the mobile station will use the second decoding algorithm or technique when it is not possible for the base station to guarantee the transmission of the sync word in subsequent time slots.

According to the decoding and demodulation techniques described in the incorporated references, a mobile station receives an assigned or allocated time slot of one TDMA frame period. Using the first decoding algorithm, the mobile station uses known symbols called the first synchronization word, which are transmitted near the beginning of the assigned time slot, and by means of the known symbol called the second synchronization word near the beginning of the subsequent time slot. The transmitted known symbols decode the received signal. Stated another way, the base station transmits a first predetermined data symbol and an unknown data symbol. A sync word or other known data pattern constitutes the first predetermined data symbol. Specific data designated for a specific mobile station are unknown data symbols. Unknown data symbols can be encoded as voice data, control data or other data. In some systems, the base station transmits a second predetermined data symbol, such as a second synchronization word, in a subsequent time slot.

In some systems, known symbols at the beginning of subsequent slots, eg, the second synchronization word, are not guaranteed to be sent by the base station. This can be achieved, for example, to reduce co-channel interference for receivers in the surrounding area. If subsequent time slots are not assigned to the base station's mobile station, the base station may suspend transmissions, including synchronization words, during the unassigned time slots to reduce co-channel interference. Alternatively, the base station may use directional antennas to allow the broadcast of time slots into specific sectors of an area served by the base station. Such a sector may be different from the sector in which the mobile station assigned the current time slot resides. Therefore, due to the change in beam direction, it is impossible for the second time slot to be received coherently with the previous time slot data.

Due to these possibilities, it is not possible for the base station to guarantee the transmission of a second predetermined data symbol, eg a synchronization word in a subsequent time slot. Also, sending a second predetermined data symbol is unlikely to be useful if it occurs that the timing or phase or amplitude of the subsequent time slot is substantially changed by the base station for any particular reason. Since the sync word is used by the mobile station to synchronize its timing and reception to the base station, any change in these parameters can cause a loss of synchronization and require the mobile station to be resynchronized to the base station.

When a known symbol, such as a synchronization word, is not guaranteed to be transmitted by the base station at the beginning of a subsequent time slot, or is not guaranteed to be consistent with the transmission in the current time slot in timing, phase, amplitude or direction, according to the present invention The base station provides a signal to the mobile station indicating that the second synchronization word cannot be relied upon. Stated another way, the base station sends an indication when the transmission of the second predetermined data symbol is not guaranteed.

The mobile station decodes the transmission from the base station using at least a first predetermined data symbol. If the signal transmitted by the base station indicates that the transmission of the second predetermined data symbol or the second synchronization word is reliable, the mobile station shall use the first predetermined data symbol, the second predetermined data symbol or both, according to " The first "algorithm incorporated into the disclosure decodes the time slots received from the base station. Any suitable algorithm or otherwise described in the incorporated references may be used.

When the mobile station receives an indication that either the second predetermined data symbol or the second synchronization word cannot be relied upon, the mobile station decodes the signal received in the selected time slot using a second decoding algorithm. The second decoding algorithm only requires known symbols that were transmitted in the selected time slot. This second decoding algorithm may be of any variant described in the above incorporated references, by constantly setting the quality of the second sync word to the lowest quality value as long as the indication that the second sync word cannot be relied upon is maintained. implement. Any other suitable decoding algorithm can also be used, using only one guaranteed sync word.

Thus when an indication is sent, the mobile station uses the first predetermined data symbol to decode the unknown data symbol, and when no indication is sent, uses the first predetermined data symbol and the second predetermined data symbol to decode the unknown data symbol. Data symbol decoding. The indication may be any suitable data or signal contained within the control signal information sent by the base station to the mobile station. In one embodiment, the indication is sent during call setup or handover. Call setup occurs when two-way communication is initiated between the mobile station and the base station. Call initiation occurs when the mobile station indicates that the user wishes to make an outgoing call or when the base station has signaled an incoming call to the mobile station on the communication channel. A handoff occurs when a mobile station moves from the coverage area of a first base station to the coverage area of a second base station. When these two situations occur, basic control information is exchanged between the mobile station and the base station.

In one embodiment, the base station broadcasts the indication to all mobile stations in its coverage area or in a sector of its coverage area. This can be accomplished using a broadcast control channel (BCCH) known as a digital control channel or DCC. This indication informs the mobile station that the base station is using a mode of operation that does not guarantee the availability of the second synchronization word. In response, all mobile stations in the sector or coverage area use the second decoding algorithm.

In another embodiment, the mobile station provides an indication to the base station that the mobile station requires a second synchronization word for optimal decoding of time slot information from the base station. This is suitable for compatibility with mobile stations having such requirements. According to this embodiment, the mobile station transmits a pointer indicating that the mobile station needs to transmit a second predetermined data symbol. In response to this pointer, the base station according to the invention reliably transmits a second predetermined data symbol even when no data is transmitted in the following time slot. The base station does not suspend the second sync word, does not change the transmission phase and amplitude or any other necessary characteristics, but may omit sending the data following the second word if no data needs to be sent.

The pointer may comprise a predetermined data pattern or an operating mode pointer for the mobile station. This pointer may be sent to the base station with control information provided by the mobile station.

Alternatively, the pointer can be included in the standard information sent by the mobile station to the base station. For example, each mobile station has a protocol version number that is sent to the base station when communication between the two is initiated. The protocol version number refers to a modification of a standard, such as IS-136, that the mobile station is using. In response to the protocol version number or any other similar pointer, the base station can decide whether the mobile station expects the second synchronization word or can be reliably operated without sending the second synchronization word. Also, one of the two operating modes can be set to a constant value with non-stationary conditions, selected only according to appropriate determination by the base station. Further, in another embodiment, the base station can determine which mode to operate by using an identifier, such as the mobile station's Electronic Serial Number (ESN), which is sent by the mobile station during call setup. By comparing the ESN for a mobile station with values stored in memory at the base station or elsewhere in the communication network, the base station can release from the subscriber database the characteristics of the mobile station, including which mode of operation is provided for the mobile station. Accordingly, the base station determines a transmission request for the mobile station, and transmits a predetermined second data symbol in response to the mobile station's transmission request.

FIG. 3 is a flowchart illustrating a method of operating a base station in the wireless communication system 100 of FIG. 1 . The method starts at step 302 and at step 304 the base station determines whether the mobile station (MS) requires a second synchronization word. This determination may be made in any suitable manner, such as by receiving signal information from the mobile station, containing an implicit pointer that the mobile station requires a second synchronization word, or receiving an identifier or other information from the mobile station and identifying The symbols are compared with stored data to determine the transmission requirements of the mobile station. In the embodiment shown in FIG. 1, the controller 110 of the base station 102 constitutes a means for determining the type of a particular mobile station with which the base station is in radio communication. Controller 110 may operate in conjunction with memory for this purpose, or in conjunction with other data processing devices of the system, such as MSC 106.

If the base station determines that the mobile station requires a second synchronization word, at step 306, the base station transmits the first time slot including the first synchronization word. In step 308, the base station transmits at least a second synchronization word. In this way, a first predetermined data symbol (first synchronization word) and a second predetermined data symbol (second synchronization word) are provided to the mobile station for Accurate demodulation and decoding of unknown data symbols sent in . In the embodiment of FIG. 1, the transmitter 112, alone or in conjunction with the controller 110, constitutes a means responsive to the type of the particular mobile station for, when the particular mobile station is of the first type, the and transmitting radio signals to a particular mobile station during at least a portion of subsequent time slots. The method then ends at step 310 .

If at step 304, the base station determines that the mobile station does not need the second synchronization word, at step 312 the base station transmits the first time slot and the first synchronization word. With respect to the embodiment of FIG. 1, transmitter 112, alone or in conjunction with controller 110 constitutes a means, responsive to a particular type of mobile station, for transmitting a radio signal to a particular mobile station during the current time slot, when a particular When the mobile station is of the second type, the radio signal is adapted to another mobile station type. Then, at step 314, the base station determines whether the second time slot (ie, the time slot immediately following the first time slot) has been allocated. If the base station is using the second time slot of the same radio channel, two-way radio communication is carried out with the second mobile station. Transmission during a second or subsequent time slot may be suspended or altered if the base station is not communicating with any mobile station during that time slot, or if the mobile station is assigned a time slot in a different direction. If the second time slot is allocated, at step 316, the base station will transmit the second time slot and the second synchronization word, which is required by the mobile station to which the second time slot is allocated.

If, at step 314, the base station determines that the second time slot is not allocated, at step 318, the base station determines whether there is a need to alter its radio transmission. Such a need would exist, for example, if the second time slot had been allocated to a different sector located in the geographical area served by the base station. If no changes are required, control passes to step 316 where the second time slot and second sync word are transmitted. However, if changes are required, at step 320 the base station makes the necessary changes in transmission and at step 322 transmits the next time slot. The method ends at step 310 .

FIG. 4 serves as a flowchart illustrating a method for operating a first type of mobile station in the wireless communication system of FIG. 1. Referring to FIG. Mobile stations of the first type require or expect a second synchronization word sent by the base station. The method starts at step 402 .

At step 404, the mobile station remains in the loop, attempting to locate a control transmission from the base station (BS). If no suitable transmission is located, the mobile station continues searching. A mobile station may attempt to initiate a call by initiating two-way radio communication with a base station, or may attempt to transfer communication from a first base station to a second base station that is located.

In the context of FIG. 1, receive path 134 constitutes a means for receiving and decoding signals from remote base stations. Analog front end 150, demodulator 152 and decoder 154 are adapted to perform these functions. The design and implementation of these circuits, including hardware and software, and alternative implementations, are more fully described in the incorporated references. The new pointer signal provided by the present invention indicates whether the base station transmission is of the first type or the second type. The first type of transmission includes symbols, such as sync words in subsequent slots, that the mobile station 130 can use to decode the base station's transmission. The second type of base station transmission does not reliably include the second synchronization word. Decoder 154, in combination with controller 138, constitutes a means responsive to indications for decoding communication signals received from base stations 102, 104 in allocated time slots during the TDMA frame period. Decoder 154 and controller 138 may be implemented as any suitable combination of hardware or software to perform these functions.

In one embodiment, once a base station has been located, at step 406 the mobile station determines to inform the base station that it needs a second synchronization word for optimal performance. In other embodiments, no specific implementation of step 406 may occur. Instead, software or other programming controls the operation of the mobile station and the next step may simply be performed, depending on the mode of operation of the mobile station.

If the mobile station does not need the second synchronization word, it can send a pointer in step 408 . As noted above, a pointer may be data or other information contained in a signal, such as a control signal. The control signal may be, for example, an Electronic Serial Number (ESN) or Mobile Identification Number (MIN) uniquely assigned to the mobile station. The pointer indicates the type of mobile station to base station. In turn, it is determined whether the base station is to transmit a second predetermined data symbol in the time slot assigned to it in the subsequent time slot. Alternatively, the pointer may be a specific class flag or protocol version number that is communicated to the base station and used by the base station to determine that the mobile station needs to transmit the second synchronization word. Further, the mobile station may only send identification information, such as an identifier similar to an electronic serial number, which is then used by the base station to determine the mobile station's transmission requirements.

In step 408, the mobile station receives the first time slot transmitted by the base station and at least the second Sync word. In step 410, the mobile station demodulates the first time slot by means of the second synchronization word. More generally, the mobile station demodulates and decodes the first time slot using any of the decoding techniques described in the above incorporated references, or any other suitable technique. The mobile station determines in step 412 whether more time slots are coming or the call has terminated. If the call continues, control returns to step 408. If the call has been terminated, the method ends at step 416.

FIG. 5 serves as a flowchart illustrating a method for operating a second type of mobile station in the wireless communication system of FIG. 1. Referring to FIG. Mobile stations of the second type do not require or expect the second synchronization word to be transmitted by the base station. However, in one embodiment, the second type of mobile station utilizes the second synchronization word to optimize its performance if the second synchronization word is available. The method starts at step 502 . Step 504 is similar to step 404, as described above in connection with the case of the first type of mobile station. In step 506, the mobile station sends an indicator that the second sync word can be omitted.

If the mobile station does not require the second synchronization word, at step 508 the mobile station of the second type may receive an indication from the base station as to whether the second synchronization word is available. In step 510, the mobile station receives a first time slot including up to a second synchronization word. In step 512, the mobile station checks whether the second sync word has been indicated as available or useful. If yes, the mobile station proceeds to step 514 and applies the first demodulation algorithm using the first and/or second synchronization word. If not, the mobile station proceeds to step 516 and demodulates the first time slot using only the first sync word using the second algorithm. Then at step 518, a soft decision is made from the subsequent first time slot whether to demodulate, deinterleave and decode using the first algorithm at step 514 or the second algorithm at step 516.

If at step 520 the call is to continue, return to step 510 to receive the next first time slot. Optionally, control returns to step 508 if each time slot indicates second sync word availability is provided, otherwise, the method ends at step 522 if the call has been terminated.

From the foregoing, it can be seen that the illustrated embodiments provide a method and arrangement for accommodating the elimination or modification of certain synchronization words transmitted by base stations in a mobile radio communication system. The base station transmits an indication to mobile stations in the area served by the base station that subsequent synchronization word transmissions will be suspended or altered and thus unreliable. In an alternative embodiment, the mobile station can send a pointer to the base station that the mobile station needs the second synchronization word, in which case the base station will continue to send the second synchronization word for use by the mobile station.

These embodiments allow the deployment of improved base stations using more advanced directional antenna arrays that can transmit different time slots of the TDMA frame cycle in different directions, adapted to the location of the designated receiver. Another approach allows the use of adaptive power control, in which time slots the transmit power level can be increased or decreased, depending on the distance to the designated receiver. These two changes affect the characteristics of the second sync word. Using the embodiment shown, these advanced base stations can be adapted to transmit a second sync word with signal continuity to previous time slots to retroactively maintain compatibility with mobile station receivers that rely on the second sync word sex.

While a particular embodiment of the invention has been shown and described, modifications can be made. For example, any pre-specified data or symbols contained in a time slot may be used by the mobile station when the sync word transmitted in each time slot has been shown for use by the mobile station in demodulating and decoding transmissions from the base station . It is therefore intended to cover in the appended claims all such changes and modifications as fall within the true spirit and scope of this invention.

Claims (25)

1. method that is used to operate the wireless communication system that comprises at least one base station and at least one mobile radio station, this method may further comprise the steps:

In the base station, send first data symbol of predesignating and unknown data symbol;

In the base station, send second data symbol of predesignating selectively;

In the base station, when transmission second data symbol of predesignating is not guaranteed, send a kind of indication;

At mobile radio station, utilize at least the first data symbol of predesignating to transmission demodulation from the base station.

2. the process of claim 1 wherein that the decoding transmission may further comprise the steps:

When indication is sent out, only utilize the decoded symbol data of first data symbol of predesignating to the unknown; With

When the nothing indication is sent out, utilize one of at least the first data symbol of predesignating and second data symbol of predesignating, to the decoded symbol data of the unknown.

3. the process of claim 1 wherein that first data symbol of predesignating comprises the synchronization character that is used for current time slots.

4. the process of claim 1 wherein that second data symbol of predesignating comprises the synchronization character that is used for follow-up time slot.

5. the process of claim 1 wherein that sending indication comprises:

In the base station,, when the transmission of synchronization character is hung up in the base station, send this indication when during follow-up time slot.

6. the process of claim 1 wherein that sending indication comprises:

When the base station can not guarantee with any reliable sequential, phase place reliably during data symbol that amplitude and direction continuity transmission reliably second reliably predesignated, sends this indication.

7. the method for claim 1 further may further comprise the steps:

At mobile radio station, send a kind of pointer, this pointer indicates the mobile radio station expectation and sends second data symbol of predesignating; With

In the base station, this pointer is responded, send second data symbol of predesignating reliably.

8. the method for claim 7, wherein this pointer comprises the data pattern of predesignating.

9. the method for claim 7, wherein pointer comprises the operator scheme pointer that is used for mobile radio station.

10. the method for claim 7, wherein this pointer comprises a kind of identifier that is used for mobile radio station and further may further comprise the steps:

In the base station, identifier is responded, be identified for the transmission requirement of mobile radio station; With

The transmission requirement that is used for mobile radio station is responded, send second data symbol of predesignating.

11. the method for claim 10 wherein sends requirement and is retrieved out from customer data base.

12. the mobile radio station that can work and be configured to receive from remote base station the first kind and second type transfers in wireless communication system, this mobile radio station comprises:

Be used for receiving and signal demodulation device from remote base station, it is the first kind or second type that this signal indicates base station transmits; With

Signal responded, and to be used for when indicating the base station be first kind when transmission, by means of in follow-up time slot from symbol that the base station sent, in time division multiple access (TDMA) frame period institute distributed time slot, to the communication signal decoding that receives from the base station, when indication indicates base station second type transfers, do not rely on the symbol that is sent in the follow-up time slot that is not assigned with, to the communication signal decoding in time slot.

13. one kind can and be configured to from the mobile radio station of the remote base station reception first kind and second type transfers in wireless communications station work, transmission being arranged in a plurality of continuous time slot, and mobile radio station comprises:

The receiver that is configured to receive transmission and produces the data that this is responded, data comprise a kind of indication, indication has first value when transmission is the first kind, is second value when transmission is second type; With

A kind of circuit of linking receiver, when indication had first value, the data that are configured to be used to from current time slots were decoded to data, when indication has second value, were configured to be used to from current time slots and subsequent timeslot data are decoded.

14. the mobile radio station of claim 13 further comprises:

Be used to transmit a signal to the transmitter of remote base station; With

Be configured the paired data format for the circuit that is sent to remote base station, data comprise a pointer, and the base station is indicated whether mobile radio station is accepted first kind transmission.

15. the mobile radio station that can work in the wireless communication system that comprises one or more base stations that send during continuous time slot, this mobile radio station comprises:

A decoder is configured to a kind of indication of identification in from the transmission of one or more base stations, indicates whether follow-up time slot can be relied on for receiving; With

A demodulator, be used for according to one of first algorithm that meets with indication and second algorithm during current time slots to transmission demodulation from one or more base stations.

16. the mobile radio station of claim 15, wherein decoder is configured to be identified in the indication in the data that receive in one or more base stations.

17. the mobile radio station of claim 16, wherein decoder is configured to identification indication from the data that one or more base stations receive between the two-way communication starting period between mobile radio station and one or more base station.

18. the mobile radio station of claim 15, wherein decoder is configured to identification indication in time slot in succession.

19. the mobile radio station of claim 18, wherein decoder is configured to during continuous time slot, and measurement is from the characteristics of signals of the transmission of one or more base stations with by identification indication that characteristics of signals and the threshold value of predesignating are made comparisons.

20. a base station that is configured to work in wireless communication system, base station are used for transmitting a signal to one or more mobile radio stations a geographic area of predesignating, mobile radio station is one of the first kind and second type, and the base station comprises:

The device that is used for the type of a definite particular mobile station of communicating by letter with base station radio; With

To the device that the type of particular mobile station responds, be used for sending:

(a) when particular mobile station is the first kind, in current time slots with at least during the part of subsequent timeslot, to the radio signal of particular mobile station; With

(b) when particular mobile station is second type, during current time slots to the wireless signal of particular mobile station be adapted to the wireless signal of another mobile radio station type.

21. the base station of claim 20, the device that wherein is used to determine comprise a circuit, this circuit is used for determining according to the transmission on the mobile radio station type of specific mobile radio station.

22. the base station of claim 20, the device that wherein is used to send adopts wireless signal, this signal is the change of the power level that transmits in the follow-up time slot, the change of the phase place of in follow-up time slot, transmitting, the variation of transmission timing in follow-up time slot, the variation of transmission direction in follow-up time slot, one of change of the change of transmission modulation and the burst format of in follow-up time slot, transmitting.

23. a time division multiple access (TDMA) radio communications system comprises:

At least one base station sends wireless signal during time slot arrives continuously, this time slot comprises current time slots and follow-up time slot, and wireless signal comprises a kind of whether follow-up time slot sends guaranteed indication;

At least one mobile radio station receives radio signals according to this indication.

24. the TDMA radio communications system of claim 23, wherein at least one mobile radio station comprises a kind of circuit when indicating follow-up slot transmission and be guaranteed, utilizes information in current time slots and the information in the subsequent timeslot that wireless signal is decoded.

25. the TDMA radio communications system of claim 23, wherein at least one base station comprises a kind of circuit, be used for indicating from least one the particular mobile station received signal of mobile radio station of the type of specific mobile radio station, mobile radio station is a kind of the needs to guarantee the type that subsequent timeslot transmits and do not need to guarantee one of type of subsequent timeslot transmission.

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