HK1100471B - Multicarrier communication system and methods for link adaptation using uniform bit loading and subcarrier puncturing - Google Patents

Description

Multi-carrier communication system and method for link adaptation using uniform bit loading and subcarrier puncturing

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No. 60/536,071 filed on 12.1.2004 as filed on title 1 (e) of U.S. code 35, which is incorporated herein by reference.

Technical Field

Embodiments of the present invention relate to electronic communications. Certain embodiments relate to wireless networks using multicarrier communication signals.

Background

A communication station ideally adapts its communications to changing channel conditions to obtain better utilization of the channel capacity. One problem with some conventional communication stations is that a large amount of feedback between the receiving station and the transmitting station is typically required to optimize channel throughput. This feedback consumes channel bandwidth and requires significant processing by the communication station. Thus, there is a general need for communication stations and methods for adapting to channel conditions that help maximize use of channel capacity while helping minimize feedback.

Brief Description of Drawings

The appended claims are directed to certain of the various embodiments of the present invention. However, the detailed description presents a more complete understanding of embodiments of the present invention when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures and:

fig. 1 is a block diagram of a multicarrier communication station in accordance with some embodiments of the present invention;

fig. 2 is a flow diagram of a subcarrier selection process in accordance with certain embodiments of the present invention;

fig. 3 is a flow diagram of a modulation level and coding rate selection process in accordance with some embodiments of the present invention; and

fig. 4 is a data rate table according to some embodiments of the invention.

Detailed Description

The following description and the drawings sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. Embodiments of the invention may be referred to herein, individually or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed.

Fig. 1 is a block diagram of a multicarrier communication station in accordance with some embodiments of the present invention. Multicarrier communication station 100 may be a wireless communication device and may transmit and/or receive wireless communication signals with transmitter circuitry 102 and/or receiver circuitry 104 using one or more antennas 106. In some embodiments, multicarrier communication station 100 may transmit multicarrier signals, such as Orthogonal Frequency Division Multiplexed (OFDM) communication signals, although the scope of the invention is not limited in this respect.

According to some embodiments, multicarrier communication station 100 may comprise subcarrier selection circuitry 110 to select active subcarriers in a multicarrier communication channel based on channel information provided by Channel State Information (CSI) processing circuitry 108. In some embodiments, multicarrier communication station 100 may also comprise modulation level and coding rate (M + C) selection circuitry 112 to select at least one of a modulation level and a coding rate for communication using active subcarriers. In some embodiments, modulation level and coding rate selection circuitry 112 may select a modulation level-coding rate combination based on the channel information and the power level selected by subcarrier selection circuitry 110 for the active subcarriers.

In some embodiments, subcarrier selection circuitry 110 may select subcarriers that are less than all of the data subcarriers of the multicarrier channel as active subcarriers. In some embodiments, this may be referred to as subcarrier puncturing because subcarriers that are not selected are not used for transmission.

In some embodiments, the number of active subcarriers and the power level, modulation level, and/or coding rate of the active subcarriers for the multicarrier channel may be selected to help maximize channel capacity based on current channel conditions, although the scope of the invention is not limited in this respect. This is described in more detail below.

In some embodiments, channel state information processing circuitry 108 may determine channel state information from communications received from a transmitting station. In some embodiments, communication station 100, as a receiving station, may determine channel state information from a channel estimate and a noise power estimate performed on a Request To Send (RTS) packet. In these embodiments, the receiving station may send a transmission instruction to the transmitting station in a Clear To Send (CTS) packet. The transmitting station may responsively transmit at least a portion of the data packet to the receiving station in accordance with the transmission instructions. In these embodiments, the transmission instructions may identify the active subcarriers and may indicate the selected power level and the selected modulation level and/or the selected coding rate.

In some embodiments, the channel state information may include one or more of a channel transfer function or an estimate thereof, one or more Radio Frequency (RF) signal characteristics, and/or one or more channel quality parameters. In some embodiments, the channel state information may include channel transfer function estimates in the frequency or time domain. In some embodiments, the channel state information may include one or more RF channel performance indicators, such as signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SINR), Received Signal Strength Indication (RSSI), and so forth. In some embodiments, the channel state information may also include one or more channel quality parameters associated with information decoded from the received signal.

In some embodiments, multicarrier communication station 100 may be referred to as a receiving station and in some embodiments communication station 100 may be referred to as a transmitting station. The term transmitting station refers to a station that is to transmit payload data, while the term receiving station refers to a station that is to receive payload data. In general, both transmitting and receiving stations may transmit and receive packets.

In some embodiments, multicarrier communication station 100 may receive and transmit packets over a wideband communication channel. A wideband channel may include one or more subchannels. The subchannels may be frequency-division multiplexed (i.e., separated in frequency from other subchannels) and may be within a predetermined frequency spectrum. The subchannels may comprise a plurality of orthogonal subcarriers. In some embodiments, the orthogonal subcarriers of a subchannel may be closely spaced OFDM subcarriers, although the scope of the invention is not limited in this respect. To achieve orthogonality between closely spaced subcarriers, in some embodiments, the subcarriers of a particular subchannel may be substantially zero at the center frequency of the other subcarriers of that subchannel.

In some embodiments, multicarrier communication station 100 may communicate with one or more other communication stations over a multicarrier communication channel. In some embodiments, the multicarrier communication channel may comprise a standard throughput channel or a high throughput communication channel. In these embodiments, the standard-throughput channel may comprise one subchannel, and the high-throughput channel may comprise a combination of one or more subchannels and one or more spatial channels associated with each subchannel. The spatial channels may be non-orthogonal channels (i.e., not separated in frequency) associated with particular subchannels in which orthogonality may be achieved through beamforming and/or diversity.

In some embodiments, the wideband channel may comprise up to four or more subchannels having a bandwidth of approximately 20MHz, and each subchannel may have up to 48 or more orthogonal data subcarriers spaced apart by approximately 312.5kHz, although the scope of the invention is not limited in this respect.

In some embodiments, the frequency spectrum for the multicarrier communication channel may comprise a 5GHz frequency spectrum or a 2.4GHz frequency spectrum. In these embodiments, the 5GHz spectrum may include frequencies ranging from approximately 4.9 to 5.9GHz, while the 2.4GHz spectrum may include frequencies ranging from approximately 2.3 to 2.5GHz, although the scope of the invention is not limited in this respect as other spectrums are equally applicable.

In some embodiments, multicarrier communication station 100 may be part of a Personal Digital Assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, or other device that may receive and/or transmit information wirelessly. In some embodiments, multicarrier communication station 100 may transmit and/or receive RF communications in accordance with particular communication standards, such as the Institute of Electrical and Electronics Engineers (IEEE) standards for Wireless Local Area Networks (WLANs), including the 802.11(a), 802.11(b), 802.11(g/h), and/or 802.11(n) standards, and/or the 802.16 standards for Wireless Metropolitan Area Networks (WMANs), although apparatus 100 may also be adapted to transmit and/or receive communications in accordance with other techniques, including the terrestrial digital video broadcast (DVB-T) broadcast standard and the high performance radio local area network (HiperLAN) standard.

Although certain embodiments of the present invention are discussed in the context of 802.11x implementations (e.g., 802.11a, 802.11g, 802.11HT, etc.), the scope of the present invention is not limited in this respect. Certain embodiments of the invention may be implemented as part of any wireless system that uses multicarrier wireless communication channels (e.g., Orthogonal Frequency Division Multiplexing (OFDM), discrete multitone modulation (DMT), etc.) such as may be used in, without limitation, Wireless Personal Area Networks (WPANs), Wireless Local Area Networks (WLANs), Wireless Metropolitan Area Networks (WMANs), Wireless Wide Area Networks (WWANs), cellular networks, third generation (3G) networks, fourth generation (4G) networks, Universal Mobile Telephone Systems (UMTS), etc. communication systems.

Antenna 106 may include one or more of a directional or omnidirectional antenna, including, for example, a dipole antenna, a monopole antenna, a loop antenna, a microstrip antenna or other type of antenna suitable for reception and/or transmission of RF signals.

Although multicarrier communication station 100 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including Digital Signal Processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, Application Specific Integrated Circuits (ASICs), and combinations of various hardware and logic circuitry for performing at least the functions described herein.

Fig. 2 is a flow diagram of a subcarrier selection process in accordance with some embodiments of the present invention. The subcarrier selection process 200 may be used to select active subcarriers of a multicarrier communication channel for subsequent communication. In some embodiments, the subcarrier selection process 200 may also determine a power level for the active subcarriers. In some embodiments, active subcarriers may be considered to be turned on, while inactive subcarriers may be considered to be turned off or punctured. In some embodiments, subcarrier selection process 200 may be performed by subcarrier selection circuitry 110 (fig. 1), although the scope of the invention is not limited in this respect.

Operation 202 comprises receiving channel state information for a multicarrier communication channel. The channel state information may be received from channel state information processing circuitry 108 (fig. 1) and may include at least an effective subcarrier noise power for each subcarrier of the multicarrier communication channel. In some embodiments, channel state information processing circuitry 108 (fig. 1) may determine channel state information from channel estimates and noise power estimates performed on received packets. In some embodiments, the effective subcarrier noise power may be the amount of additive noise power on a subcarrier divided by the square of the magnitude of the channel transfer function for that subcarrier. Additive noise power may be caused by internal noise of the receiver circuitry as well as external interference. In some embodiments, channel state information processing circuitry 108 (fig. 1) may directly estimate the effective subcarrier noise power during reception of a packet, although the scope of the invention is not limited in this respect.

Operation 204 comprises ordering the subcarriers of the multicarrier communication channel based on their effective noise powers.

Operation 206 comprises initially selecting a set of active subcarriers. In some embodiments, all subcarriers of the multi-carrier communication channel may be initially selected. In other embodiments, subcarriers having an effective subcarrier noise power below a predetermined threshold may be selected into the active set.

Operation 208 comprises setting a power level for the active subcarriers. In some embodiments, operation 208 may comprise setting the power level of each subcarrier of the active set to the total transmit power divided by the number of active subcarriers. Total transmitted power (P)_total) May be the actual transmit power level used by the transmitting station to transmit the current packet to the receiving station. In some embodiments, the total transmit power may be provided to the receiving station in the service field of the current packet, although the scope of the invention is not limited in this respect.

In certain embodiments, operation 208 may comprise basing a transmitter power budget (P)_max) Setting active set by dividing by number of active subcarriersPower level of each subcarrier. The transmitter power budget may be an available maximum transmitter power that may be used by the transmitting station. In some embodiments, the transmitter power budget (P)_max) The receiving station may be provided in the service field of the current packet, although the scope of the invention is not limited in this respect.

In some embodiments, operation 208 may comprise a total transmit power (P) based on the new request^req _total) The power level of each subcarrier of the active set is set by dividing by the number of active subcarriers. Total transmit power (P) of new request^req _total) May be provided by the receiving station based on the actual total transmit power and the transmitter power budget (P) provided to the receiving station in the service field of the current packet_max) Calculated on the basis of throughput maximization, power conservation, and/or interference minimization (for other reasons), although the scope of the invention is not limited in this respect.

In some embodiments, the total transmit power and/or transmitter power budget (P) used by a transmitting station to transmit a current packet to a receiving station_max) May be unknown to the receiving station. In these embodiments, the power levels of the subcarriers of the active set may be set to these possible parameters by relative values.

In certain embodiments, operation 208 may comprise setting the power level of each subcarrier of the active set based on (e.g., not exceeding) the maximum power spectral density. The maximum power spectral density may be predetermined by a regulatory authority. In some embodiments, when based on total transmit power (P)_total) And/or transmitter power budget (P)_max) To set the power level of the subcarriers, the power level may be set to not exceed the maximum power spectral density, although the scope of the invention is not limited in this respect. In certain embodiments, the predetermined maximum power spectral density may be determined by a regulatory authority, such as the Federal Communications Commission (FCC) in the united states, although the scope of the invention is not limited in this respect.

Operation 210 comprises calculating a channel capacity based on the power level selected in operation 208 and the effective subcarrier noise power for each active subcarrier. In some embodiments, operation 210 may calculate the channel capacity by adding the individual subcarrier capacities for each subcarrier in the active set. In some embodiments, the individual subcarrier capacities may be calculated based on the selected power level divided by the effective subcarrier noise power of the associated subcarriers in the active set squared. In some embodiments, the channel capacity may be calculated based on the following formula:

in this expression, each subcarrier of the active set (i.e., active subcarriers 1 to n) is summed, "Δ F" represents the subcarrier frequency spacing, "P" represents the subcarrier frequency spacing_n"represents the selected power level of the nth subcarrier," σ_n ²"denotes the effective subcarrier noise power of the nth subcarrier, and" Γ "denotes a predetermined subcarrier signal-to-noise ratio gap.

Operation 212 comprises decrementing the number of active subcarriers in the set. In some embodiments, the subcarrier with the worst (i.e., highest) effective subcarrier noise power may be removed from the set of active subcarriers. The subcarrier with the worst effective subcarrier noise power may be based on the ordered subcarriers of operation 204.

Operation 214 comprises resetting the power level of the remaining active subcarriers in the group and recalculating the channel capacity. In operation 214, a total amount of power may be allocated among the remaining subcarriers of the active set.

Operation 216 compares the recalculated channel capacity with the channel capacity calculated prior to decrementing the number of active subcarriers in operation 212. When the channel capacity is not increased, operation 218 is performed. As the channel capacity increases, operations 212 and 214 may be repeated until the channel capacity no longer increases to determine the final set of active subcarriers. In some embodiments, the final set of active subcarriers may provide the highest calculated channel capacity, although the scope of the invention is not limited in this respect.

In certain embodiments, the power levels of the remaining active subcarriers may be incremented in operation 214 to not exceed the predetermined maximum power spectral density obtained during the transmission of all active subcarriers. In some embodiments, to determine the final set of active subcarriers, the next worst subcarrier may be removed from the active set in operation 212 and the power level of the remaining active subcarriers may be incremented in operation 214. The increasing power level may increase the capacity of the individual subcarriers remaining in the active set, which may provide an increase in the total channel capacity. In some embodiments, subcarriers may be removed from the active set until the channel capacity no longer increases.

In operation 218, the final set of active subcarriers determined in operation 212 and the power level set in operation 214 are selected.

In some embodiments, the number of active subcarriers may be adjusted (in operation 212 or operation 212) based on interleaving requirements and/or the ability to adjust interleaving parameters. For example, in some embodiments, the subcarriers may be punctured (i.e., turned off) in groups such that the block interleaving pattern may reduce the number of rows (or columns) of its interleaver matrix by an integer, such as 1. In some embodiments, the number of subcarriers in a group may be based on the bit spacing achieved by the interleaver. For example, in a data transmission system having 48 data subcarriers, the interleaver uses 16 columns and 3 × N_bpscIn a multi-carrier communication system with a matrix of rows (3 times the number of bits per subcarrier), the adjacent bit spacing may be 3, so that the set of three subcarriers may be turned off, which may reduce the number of columns of the interleaver matrix by 1.

In some embodiments, the total transmit power (P) when the transmitting station is to transmit the current packet to the receiving station_total) And/or transmitter power budget (P)_max) The power levels of the subcarriers of the active set, when unknown to the receiving station, may be set to the relative values of these possibly unknown parameters, and the receiving station provides the recommended power levels of the subcarriers to the transmitter in operation 218. In some embodiments, the number of active subcarriers, the power level, the modulation level, and the coding rate are allCan be optimized together. This will be discussed in more detail below.

Fig. 3 is a flow diagram of a modulation level and coding rate selection process according to some embodiments of the invention. Modulation level and coding rate selection process 300 may be used to select a modulation level and/or a coding rate to facilitate maximizing channel throughput using the active subcarriers determined in process 200 (fig. 2) and the power level determined in process 200 (fig. 2). In some embodiments, process 300 may select the same modulation level and/or coding rate for all active subcarriers (i.e., referred to as uniform bit loading), although the scope of the invention is not limited in this respect. In some embodiments, process 300 may be performed using modulation level and coding rate selection circuitry 112 (fig. 1), although the scope of the invention is not limited in this respect. In some embodiments, process 300 may select a modulation level and/or a coding rate for the active subcarriers based on the most recently calculated channel capacity and power level.

In some embodiments, the same power level, modulation level, and coding rate may be selected for the active subcarriers, while the inactive subcarriers may be turned off. In other embodiments, the same modulation level and coding rate may be selected for the active subcarriers, however different power levels may be selected for the active subcarriers corresponding to different frequency subchannels or spatial channels, e.g., based on the noise power levels of the active subcarriers or to help maximize throughput and/or channel capacity, although the scope of the invention is not limited in this respect. In other embodiments, different power levels, modulation levels, and/or coding rates may be selected for the active subcarriers to help maximize throughput or channel capacity, although the scope of the invention is not limited in this respect.

Operation 302 comprises calculating a subcarrier signal-to-noise ratio for each active subcarrier based on the selected power level of the associated subcarrier and the effective subcarrier noise power. The selected power level may ultimately be determined at operation 218 (fig. 2) of process 200 (fig. 2).

Operation 304 comprises calculating an effective subcarrier capacity for each active subcarrier based on the calculated subcarrier signal-to-noise ratio for the associated subcarrier. The effective subcarrier capacity need not correspond to the effective subcarrier capacity used in operation 204 (fig. 2). In some embodiments, the effective subcarrier capacity for each effective subcarrier may be substantially calculated by multiplying the subcarrier frequency spacing by one plus the logarithm of the signal-to-noise ratio (SNR) of the associated active subcarrier divided by the predetermined subcarrier SNR gap, although the scope of the invention is not limited in this respect. The predetermined subcarrier SNR gaps of operation 304 do not necessarily correspond to the predetermined subcarrier SNR gaps used in operation 214 (fig. 2). In some embodiments, the effective subcarrier capacity for each active subcarrier may be calculated using the following expression:

effective subcarrier capacity C_k＝ΔF·log₂(1+γ_k/Γ)

In this expression, the effective subcarrier capacity C may be calculated for each subcarrier of the active set (i.e., active subcarriers 1 to k)_k"Δ F" represents a subcarrier frequency spacing, "γ_k"denotes the signal-to-noise ratio of the kth subcarrier, and" Γ "denotes a predetermined subcarrier signal-to-noise ratio gap.

Operation 306 comprises calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers. In certain embodiments, operation 306 may calculate an average of the effective subcarrier capacities calculated in operation 304.

Operation 308 comprises selecting a modulation level-coding rate combination for the subcarriers in the active set that provides a data rate that is close or closest to the average effective subcarrier capacity. In certain embodiments, operation 308 comprises selecting a modulation level and a coding rate for the subcarriers in the active set by determining a modulation level and a coding rate that provide a data rate per subcarrier (i.e., the number of information bits per second per subcarrier) that is at least slightly greater than the average effective subcarrier capacity (i.e., a higher data rate). In these embodiments, operation 308 further comprises determining a modulation level and a coding rate that provides a data rate per subcarrier (i.e., the number of information bits per second per subcarrier) that is at least slightly less than the average effective subcarrier capacity (i.e., a lower data rate).

In certain embodiments, the modulation stages comprise Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 8PSK, 16-quadrature amplitude modulation (16-QAM), 32-QAM, 64-QAM, 128-QAM, and 256-QAM. In certain embodiments, the coding rates include Forward Error Correction (FEC) coding rates 1/2, 2/3, 3/4, 5/6, and 7/8. An example of certain modulation level-coding rate combinations for various data rates is shown in fig. 4.

Operation 310 comprises calculating a first number of active subcarriers having a capacity higher than the higher data rate. Operation 310 also comprises calculating a second number of active subcarriers having a capacity lower than the lower data rate.

Operation 312 comprises selecting a modulation level and a coding rate associated with the higher data rate when the difference between the first and second numbers calculated in operation 310 is greater than a predetermined percentage of active subcarriers. Operation 312 further comprises selecting a modulation level and a coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers.

Operation 314 generates a transfer instruction. In some embodiments, the transmission instructions may identify the active subcarriers (or groups of active subcarriers) selected in process 200 (fig. 2), the power level selected in process 200 (fig. 2), and the modulation level and coding rate selected in operation 312. In some embodiments, the transmission instructions may identify punctured subcarriers or groups of punctured subcarriers, although the scope of the invention is not limited in this respect. In some embodiments, the power level selected in process 200 (fig. 2) may be identified in absolute value (e.g., in dBm), while in other embodiments, the power level may be identified in relative value to the actual transmit power level used to transmit the current packet. In some embodiments, the transmission instructions may identify individual power levels for each active subcarrier or group of active subcarriers, although the scope of the invention is not limited in this respect. In some embodiments, the transmission instructions may identify individual modulation levels and/or coding rates for each active subcarrier or group of active subcarriers, although the scope of the invention is not limited in this respect. In some embodiments, the receiving station may send the transmission instruction to the transmitting station in a Clear To Send (CTS) packet, although the scope of the invention is not limited in this respect.

In certain embodiments, processes 200 (fig. 2) and 300 may be performed on a periodic basis. In some embodiments, processes 200 (fig. 2) and 300 may be performed on a per packet basis to determine communication parameters for a next packet, although the scope of the invention is not limited in this respect. In some embodiments, processes 200 (fig. 2) and 300 may be performed frequently enough to account for time differences of the channels.

Although the individual operations of procedures 200 (fig. 2) and 300 are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated.

Fig. 4 is a data rate table according to some embodiments of the invention. Column 402 of table 400 lists examples of possible data rates (in bits per second), column 404 lists modulation types, and column 406 lists Forward Error Correction (FEC) coding rates. For any particular row, the data rate of column 402 may correspond to the associated modulation and coding rate of columns 404 and 406, respectively. In some embodiments, more or less data rates than shown in table 400 may be used. The indexed data rates in column 408 are examples of possible data rates that may be selected for use in operation 308 (fig. 3). In some embodiments, other data rates may be indexed, and the use of only 8 indices is not required.

Unless specifically stated otherwise, terms such as processing, computing, calculating, determining, displaying, or the like, may refer to an action and/or process of one or more processing or computing systems or similar devices that may manipulate and transform data represented as physical (e.g., electronic) quantities within a processing system's registers and memory into other data similarly represented as physical quantities within the processing system's registers or memories, or other such information storage, transmission or display devices. Further, as used herein, a computing device includes one or more processing elements coupled with computer-readable memory that may be volatile or non-volatile memory or a combination thereof.

Embodiments of the invention may be implemented in one or a combination of hardware, firmware, and software. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by at least one processor to perform the operations described herein. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others.

The abstract is provided to comply with section 1.72(b) of the 37 c.f.r., which is an abstract that requires a technical disclosure to allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims.

In the foregoing detailed description, various features may occasionally be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the subject matter require more features than are expressly recited in each claim. Rather, as the following claims reflect, invention lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment.

Claims (35)

1. A multi-carrier communication method, comprising:

setting a power level for a set of active subcarriers based on a number of active subcarriers of a multicarrier communication channel;

calculating a channel capacity based on the power level of each active subcarrier and the effective subcarrier noise power;

decrementing the number of active subcarriers in the set of active subcarriers and re-performing the setting and calculating to determine a final set of active subcarriers that provides the highest calculated channel capacity; and

selecting at least one of a modulation level and a coding rate for the active subcarriers based on the calculated channel capacity, comprising:

calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers;

determining a first modulation level and a first coding rate that provide a higher data rate that is at least slightly greater than the average effective subcarrier capacity;

determining a second modulation level and a second coding rate that provide a lower data rate that is at least slightly less than the average effective subcarrier capacity;

calculating a first number of active subcarriers having a capacity higher than the higher data rate;

calculating a second number of active subcarriers having a capacity lower than the lower data rate;

selecting a first modulation level and a first coding rate associated with the higher data rate when the difference between the first and second numbers is greater than a predetermined percentage of active subcarriers; and

selecting a second modulation level and a second coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers.

2. The method of claim 1, wherein the setting the power level further comprises incrementing the power level for each active subcarrier after one or more subcarriers are removed from the set of active subcarriers.

3. The method of claim 2, further comprising ordering the subcarriers based on effective subcarrier noise power; and

wherein decrementing the number of active subcarriers in the set of active subcarriers comprises removing one of the subcarriers having the next largest effective subcarrier noise power from the set of active subcarriers before resetting the power level of the remaining subcarriers and recalculating the channel capacity.

4. The method of claim 3, further comprising initially selecting subcarriers for the set of active subcarriers having an effective subcarrier noise power below a predetermined threshold.

5. The method of claim 2, further comprising initially selecting substantially all subcarriers into the set of active subcarriers.

6. The method of claim 2, wherein the setting comprises setting a power level for each subcarrier of the set of active subcarriers to a total transmit power divided by a number of active subcarriers, the total transmit power being an actual transmit power level used to transmit a current packet.

7. The method of claim 2, wherein the setting comprises setting a power level for each subcarrier of the set of active subcarriers based on a transmitter power budget divided by a number of active subcarriers, the transmitter power budget being an available transmitter power for a transmitting station.

8. The method of claim 2, wherein the setting comprises setting a power level for each subcarrier of the set of active subcarriers based on a maximum power spectral density, wherein the maximum power spectral density is predetermined by a regulatory authority.

9. The method of claim 1, wherein the calculating the channel capacity comprises adding individual subcarrier capacities for each subcarrier in the set of active subcarriers,

wherein the individual subcarrier capacities are calculated based on the set power levels divided by the effective subcarrier noise powers of the associated subcarriers of a set of active subcarriers.

10. The method of claim 1, wherein said selecting at least one of a modulation level and a coding rate further comprises:

calculating a subcarrier signal-to-noise ratio for each active subcarrier based on the selected power level and the effective subcarrier noise power for the associated subcarrier; and

an effective subcarrier capacity is calculated for each active subcarrier based on the calculated subcarrier signal-to-noise ratio for the associated subcarrier.

11. The method of claim 1, further comprising determining channel state information for the multicarrier communication channel, the channel state information comprising at least an effective subcarrier noise power for an individual subcarrier or a group of subcarriers.

12. The method of claim 1, further comprising transmitting the selected set of active subcarriers, the selected power level, the selected modulation level, and the selected coding rate to a transmitting station for transmitting a next packet.

13. The method of claim 12, further comprising receiving a next packet from the transmitting station, the next packet transmitted using the selected set of active subcarriers according to the selected power level, the selected modulation level, and the selected coding rate.

14. The method of claim 1, wherein the multicarrier communication channel comprises a standard-throughput channel or a high-throughput communication channel, the standard-throughput channel comprising a subchannel and the high-throughput channel comprising a combination of one or more subchannels and one or more spatial channels associated with each subchannel.

15. The method of claim 14, wherein the high-throughput communication channel comprises one of:

a wideband channel having up to four frequency-separated subchannels;

a multiple-input multiple-output (MIMO) channel comprising a single subchannel having up to four spatial subchannels; and

a wideband MIMO channel comprising two or more frequency separated subchannels, wherein each subchannel has two or more spatial channels.

16. The method of claim 14, wherein the one or more spatial channels and the one or more subchannels are provided by one or more transmit antennas of a transmitting station when the multicarrier communication channel is a high-throughput communication channel.

17. The method of claim 14, wherein subcarriers of an associated subchannel are substantially zero at center frequencies of other subcarriers to achieve substantial orthogonality between subcarriers of the associated subchannel.

18. A multi-carrier communication station, comprising:

radio frequency circuitry to transmit radio frequency signals over a multicarrier communication channel;

subcarrier selection circuitry for selecting a set of active subcarriers of the multicarrier communication channel by decrementing the number of active subcarriers in the set and incrementing the power level of the remaining active subcarriers to obtain a highest channel capacity; and

a modulation level and coding rate selection circuit for:

calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers;

determining a first modulation level and a first coding rate that provide a higher data rate that is at least slightly greater than the average effective subcarrier capacity;

determining a second modulation level and a second coding rate that provide a lower data rate that is at least slightly less than the average effective subcarrier capacity;

calculating a first number of active subcarriers having a capacity higher than the higher data rate;

calculating a second number of active subcarriers having a capacity lower than the lower data rate;

selecting a first modulation level and a first coding rate associated with the higher data rate when the difference between the first and second numbers is greater than a predetermined percentage of active subcarriers; and

selecting a second modulation level and a second coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers.

19. The communication station of claim 18, wherein the subcarrier selection circuit sets a power level for active subcarriers based on the number of active subcarriers, calculates a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier, removes active subcarriers from the set of active subcarriers, increments the power levels of the remaining active subcarriers, and recalculates the channel capacity to determine a final set of active subcarriers that provides the highest calculated channel capacity.

20. The communication station of claim 18, wherein the subcarrier selection circuit orders the subcarriers based on effective subcarrier noise power and removes one of the subcarriers having the next largest effective subcarrier noise power from the set of active subcarriers before incrementing the power levels of the remaining subcarriers and recalculating the channel capacity.

21. The communication station of claim 20, wherein the subcarrier selection circuit initially selects subcarriers for the set of active subcarriers having an effective subcarrier noise power below a predetermined threshold.

22. The communication station of claim 19, wherein the subcarrier selection circuit initially selects substantially all subcarriers into the set of active subcarriers.

23. The communication station of claim 19, wherein the subcarrier selection circuit sets the power level of each subcarrier of the set of active subcarriers to a total transmit power divided by the number of active subcarriers, the total transmit power being an actual transmit power level used to transmit a current packet to the communication station in a service field of the current packet.

24. The communication station of claim 19, wherein the subcarrier selection circuit sets the power level for each subcarrier of the set of active subcarriers based on a transmitter power budget divided by the number of active subcarriers, the transmitter power budget being available transmitter power for a transmitting station.

25. The communication station of claim 19, wherein the subcarrier selection circuit sets the power level for each subcarrier of the set of active subcarriers based on a maximum power spectral density, wherein the maximum power spectral density is determined by a regulatory authority.

26. The communication station of claim 18, wherein the subcarrier selection circuit calculates the channel capacity by adding individual subcarrier capacities for each subcarrier in the set of active subcarriers,

wherein the subcarrier selection circuitry calculates the individual subcarrier capacities based on the set power levels divided by effective subcarrier noise powers of associated subcarriers of the set of active subcarriers.

27. The communication station of claim 19, wherein the radio frequency circuitry includes receiver circuitry to determine channel state information for the multicarrier communication channel, the channel state information including at least an effective subcarrier noise power for an individual subcarrier or group of subcarriers.

28. The communication station of claim 18, wherein the radio frequency circuitry comprises transmitter circuitry to send an instruction to the transmitting station to transmit a next packet comprising the selected set of active subcarriers, the selected power level, the selected modulation level, and the selected coding rate.

29. The communication station of claim 28, wherein the radio frequency circuitry includes receiver circuitry to receive a next packet from the transmitting station, the next packet transmitted using the selected set of active subcarriers according to the selected power level, the selected modulation level, and the selected coding rate.

30. The communication station of claim 18, wherein the multicarrier communication channel comprises a standard-throughput channel or a high-throughput communication channel, the standard-throughput channel comprising one subchannel and the high-throughput channel comprising a combination of one or more subchannels and one or more spatial channels associated with each subchannel.

31. A multi-carrier communication system comprising:

a substantially omni-directional antenna;

radio frequency circuitry coupled to the antenna for transmitting radio frequency signals over a multicarrier communication channel; and

subcarrier selection circuitry for selecting a set of active subcarriers of the multicarrier communication channel by decrementing the number of active subcarriers in the set and incrementing the power level of the remaining active subcarriers to obtain a highest channel capacity; and

a modulation level and coding rate selection circuit for:

calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers;

determining a first modulation level and a first coding rate that provide a higher data rate that is at least slightly greater than the average effective subcarrier capacity;

determining a second modulation level and a second coding rate that provide a lower data rate that is at least slightly less than the average effective subcarrier capacity;

calculating a first number of active subcarriers having a capacity higher than the higher data rate;

calculating a second number of active subcarriers having a capacity lower than the lower data rate;

selecting a first modulation level and a first coding rate associated with the higher data rate when the difference between the first and second numbers is greater than a predetermined percentage of active subcarriers; and

selecting a second modulation level and a second coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers.

32. The system of claim 31 wherein the subcarrier selection circuit sets a power level for the active subcarriers based on the number of active subcarriers, calculates a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier, removes active subcarriers from the set of active subcarriers, increments the power levels of the remaining active subcarriers, and recalculates the channel capacity to determine a final set of active subcarriers that provides the highest calculated channel capacity.

33. A multi-carrier communication device, comprising:

means for setting a power level for a set of active subcarriers of a multicarrier communication channel based on a number of active subcarriers;

means for calculating a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier;

means for decrementing the number of active subcarriers in the set of active subcarriers and re-performing the setting and calculating to determine a final set of active subcarriers that provides the highest calculated channel capacity; and

means for selecting at least one of a modulation level and a coding rate for the active subcarriers based on the calculated channel capacity, comprising:

means for calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers;

means for determining a first modulation level and a first coding rate that provide a higher data rate that is at least slightly greater than the average effective subcarrier capacity;

means for determining a second modulation level and a second coding rate that provide a lower data rate that is at least slightly less than the average effective subcarrier capacity;

means for calculating a first number of active subcarriers having a capacity above the higher data rate;

means for calculating a second number of active subcarriers having a capacity lower than the lower data rate;

means for selecting a first modulation level and a first coding rate associated with the higher data rate when the difference between the first and second numbers is greater than a predetermined percentage of active subcarriers; and

means for selecting a second modulation level and a second coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers.

34. The apparatus of claim 33, further comprising:

means for setting the power level further comprises incrementing the power level for each active subcarrier after one or more subcarriers are removed from the set of active subcarriers; and

means for ordering the subcarriers based on effective subcarrier noise power,

wherein the means for decrementing the number of active subcarriers in the set of active subcarriers comprises means for removing one of the subcarriers having the next largest effective subcarrier noise power from the active subcarriers before resetting the power level of the remaining subcarriers and recalculating the channel capacity.

35. A method for selecting transmission parameters of a multi-carrier communication channel, comprising:

setting a power level for a set of active subcarriers of a multicarrier communication channel based on a number of the active subcarriers;

calculating a channel capacity based on the power level and an effective subcarrier noise power for each active subcarrier;

decrementing the number of active subcarriers in the set of active subcarriers and re-performing the setting and calculating to determine a final set of active subcarriers that provides the highest calculated channel capacity; and

selecting at least one of a modulation level and a coding rate for the active subcarriers based on the calculated channel capacity, comprising:

calculating an average effective subcarrier capacity based on the effective subcarrier capacities of the active subcarriers;

determining a first modulation level and a first coding rate that provide a higher data rate that is at least slightly greater than the average effective subcarrier capacity;

determining a second modulation level and a second coding rate that provide a lower data rate that is at least slightly less than the average effective subcarrier capacity;

calculating a first number of active subcarriers having a capacity higher than the higher data rate;

calculating a second number of active subcarriers having a capacity lower than the lower data rate;

selecting a first modulation level and a first coding rate associated with the higher data rate when the difference between the first and second numbers is greater than a predetermined percentage of active subcarriers; and

selecting a second modulation level and a second coding rate associated with the lower data rate when the difference between the first and second numbers is less than or equal to a predetermined percentage of active subcarriers,

wherein further comprising ordering the subcarriers based on effective subcarrier noise power, an

Wherein decrementing the number of active subcarriers in the set of active subcarriers comprises removing one of the subcarriers having the next largest effective subcarrier noise power from the set of active subcarriers before resetting the power level of the remaining subcarriers and recalculating the channel capacity, and

wherein the selecting at least one of a modulation level and a coding rate further comprises:

calculating a subcarrier signal-to-noise ratio for each active subcarrier based on the selected power level and the effective subcarrier noise power for the associated subcarrier; and

an effective subcarrier capacity is calculated for each active subcarrier based on the calculated subcarrier signal-to-noise ratio for each associated subcarrier.