HK1148420A - Cross-layer multi-packet reception based medium access control and resource allocation - Google Patents

Description

Cross-layer multi-packet reception based on medium access control and resource allocation

Technical Field

The subject disclosure relates to wireless network communications, and more particularly, to wireless network-based multiple-input multiple-output and single-input multiple-output.

Background

Wireless networks (WLANs), such as IEEE802.11 based Wireless Local Area Networks (WLANs), are becoming popular and widely deployed. However, existing WLANs generally operate away from the theoretical limit, especially in high network load situations. One of the main reasons for this is that these systems are designed based on a hierarchical approach that is generally not efficient. In particular, a medium access control protocol is designed without considering the characteristics of a physical layer. At the same time, physical layer resources are generally not well utilized because medium access control issues are not considered.

For example, the medium access control protocols (e.g., 802.11a, 802.11b, 802.11g) in existing 802.11 based systems use a simplified collision model that supports only one synchronous transmission. In particular, 802.11 based systems are based on the carrier sense multiple access protocol with collision avoidance (CSMA/CA). Such an idealized model has both advantages and disadvantages. This model is advantageous because there is an assumption of error-free reception that ignores channel effects such as fading and noise. However, this model is disadvantageous because it cannot take advantage of the capabilities of the physical layer to successfully decode multiple packets in the presence of synchronous transmissions. Recently, there has been a great interest in IEEE802.11n standardization efforts to improve throughput by deploying multiple antennas. However, with the previous 802.11-based collision model, its collision model remains substantially unchanged and does not allow for multi-packet reception.

One possible solution to enable multi-packet reception is to deploy adaptive antenna arrays, or Multiple Input Multiple Output (MIMO) technology, at both the transmitter and receiver ends to allow Spatial Division Multiple Access (SDMA). One particular case of MIMO is Single Input Multiple Output (SIMO) with a single transmit antenna and multiple receive antennas. On the other hand, Orthogonal Frequency Division Multiplexing (OFDM) is used in most current 802.11 systems for its performance to efficiently utilize limited RF bandwidth and transmit power in broadband transmission over time-diverse multiplexed channels. Multi-user OFDM, or Orthogonal Frequency Division Multiple Access (OFDMA), is another alternative to implementing multi-packet reception. The inherent multicarrier nature of OFDMA systems also allows dynamic subcarrier allocation in combination with adaptive bit loading and power control, thereby enabling an increase in achievable data rates through the exploitation of frequency and multiuser dispersion. Also for broadband wireless systems, the use of MIMO technology in combination with OFDM is an attractive solution.

However, existing conventions for resource allocation are not well suited for 802.11-like systems, and most conventions do not consider medium access control issues. In addition, for multi-user MIMO/OFDM systems, the existing allocation methods are very incomplete solutions.

For example, there are two main techniques in MIMO systems that utilize transmit antenna arrays: space-time coding and transmit beamforming. These two strategies are based on two different and extreme assumptions about the channel feedback available at the transmitter. Space-time coding does not require feedback, whereas existing beamforming requires accurate feedback. The disadvantages of space-time coding are significant in terms of its assumptions, and are rarely valid for existing beamforming assumptions.

The above description of the deficiencies of MIMO-based wireless networks is intended only to generally point out some of the problems of current MIMO-based wireless networks and is not intended to be exhaustive. Other problems with the current state of the art will become more apparent when the following description of various non-limiting embodiments is read in detail.

Disclosure of Invention

A brief summary is provided herein to facilitate a basic or general understanding of various aspects of exemplary, non-limiting embodiments that follow in the more detailed description and the accompanying drawings. This summary is not intended as an extensive or exhaustive description. Rather, the sole purpose of this summary is to present concepts related to certain exemplary, non-limiting embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later for various embodiments of the invention.

Cross-layer multi-packet reception medium access control and resource allocation techniques are provided for wireless networks having receivers using multiple antennas. After a random backoff (backoff) time, the ue on the wireless network accesses the network for data transmission by making a Request To Send (RTS) Request. In response to the request transmission, the access point (or other receiver) determines transmission parameters that optimize use of the physical layer. The transmitter parameters may include subcarriers, bits, and power allocation information. Those transmission parameters are sent from the receiver To the indicated transmitter along with a Clear To Send (CTS) message. Upon receiving the CTS message, data is transmitted according to the transmission parameters.

Drawings

The system and method for cross-layer multi-packet reception medium access control and resource allocation will be further described with reference to the accompanying drawings in which:

fig. 1 illustrates a MIMO wireless network operating environment;

FIG. 2 illustrates a protocol operation according to one embodiment;

FIG. 3 is an exemplary transmitter during data transmission;

FIG. 4 is an exemplary receiver during data transmission;

FIG. 5 illustrates the structure of a space-time coded beamformer according to one embodiment;

FIG. 6 illustrates the relationship between ρ and bit error rate in various resource allocation techniques;

FIG. 7 is a diagram illustrating the relationship between signal-to-noise ratio per subcarrier and average number of OFDM symbols per packet in various resource allocation techniques;

FIG. 8 is a graph illustrating the relationship between signal-to-noise ratio per subcarrier and throughput in various resource allocation techniques;

FIG. 9 is a diagram illustrating the relationship between the number of users and throughput for various resource allocation techniques;

FIG. 10 is a graph illustrating the relationship between packet arrival rate and average packet delay in various resource allocation techniques;

FIG. 11 is a graph illustrating the relationship between the signal-to-noise ratio per subcarrier and the average packet delay in various resource allocation techniques;

FIG. 12 is a diagram illustrating the relationship between packet arrival rate and throughput in various resource allocation techniques;

FIG. 13 illustrates an exemplary system according to one embodiment;

fig. 14 is a flow chart of an exemplary method performed by a user equipment transmitter according to one embodiment;

FIG. 15 is a flow chart of an exemplary method performed by a receiver according to one embodiment;

FIG. 16 is a block diagram representing an exemplary non-limiting computing system or operating environment in which the present invention may be implemented.

Detailed Description

SUMMARY

As discussed in the "background" section, existing medium access and resource allocation techniques for multi-user MIMO (and other multi-user multi-antenna systems such as SIMO) systems are inefficient. One of the reasons for this inefficiency is the challenge faced behind the resource allocation problem of such systems. For example, the quantization and processing of co-channel interference is not trivial because it depends on the transmission scheme and detection technique at the receiver, the accuracy of the channel information, the spatial independence of the users, and the transmission capabilities of all allowed users. As a second example, the selection of the user set for each subcarrier typically requires a combined search for the best solution, which makes the allocation quite complex.

Referring to fig. 1, fig. 1 illustrates an exemplary wireless network 100. Although a simple wireless local area network is illustrated for simplicity, it will be recognized that the techniques may also be used for wireless networks of different sizes and more complex local area networks. Fig. 1 also illustrates that various user devices (104, 106, 108) (hereinafter, they are simply referred to as users) are connected to the network. In some embodiments, any user device, such as a game console, handheld computer, laptop 106, smartphone 104, personal digital assistant 108, desktop computer, or embedded computer in a household appliance (e.g., microwave oven or refrigerator) may be attached to the wireless network. The device may have an internal connection to the wireless network or may be connected to an external device that connects it to the wireless network, such as an Ethernet (Ethernet) connected to a wireless adapter. In this illustration, each user is in wireless communication with the access point 102. It will be appreciated that in other embodiments, the wireless network may include multiple access points. Additionally, it will be recognized that in other embodiments, the wireless network may also operate in a peer-to-peer mode rather than an infrastructure mode. The access point and the user equipment each have multiple antennas.

Typically, the access point 102 is connected to a wired network 110, such as an ethernet network. It will be appreciated, however, that the ap may also be connected to a second wireless network. Various servers 112 may be connected to the wired network and provide various services (e.g., file services, email, Web portals, print servers, etc.). Although not shown in the drawings, other devices such as a network printer or scanner may be connected via a wired network. Typically, the wired network is also connected to a wide area network 114, such as the Internet.

MIMO/OFDM based WLAN embodiments

The following notation was used. (.)^*、(·)^TAnd (.)^HRespectively, conjugate, transpose, and Hermitian conjugate (Hermitian) transpose. | represents a complex norm. E | represents the desired operation and CN (μ Σ) represents a complex Gaussian distribution with mean μ and covariance matrix Σ.

For the sake of brevity, the exemplary embodiments are considered in the context of a simplified MIMO/OFDM-based WLAN. However, it will be recognized that cross-layer medium access control and resource allocation may also be used in other types of multi-packet receiving wireless networks. In particular, in case that a plurality of mobile users or nodes communicate with one Access Point (AP), uplink transmission of the MIMO/OFDM based WLAN system is considered. In this example case, there is a total of K in the system_tUsers, each user being provided with M_tA transmitting antenna, AP is equipped with M_rA receiving antenna. A characteristic of the medium access control protocol is that it incorporates adaptive resource allocation into the protocol through the use of RTS/CTS exchanges. Thus, thisThe multi-packet reception performance in the illustrated embodiment stems not only from the use of SDMA, but also from the use of OFDMA.

The protocol operation according to one embodiment is illustrated in fig. 2. Before the user initiates a transmission, he senses the channel to determine if there are any pending transmissions. If the medium is found to be idle for an interval exceeding the distributed intra space (DIFS), then each user is selected to be at [0, CW-1 ]]A random backoff counter value uniformly distributed within an interval, wherein the CW represents a contention window (contention window), the CW is maintained in units of slots, and initially set to the CW_min. After the random backoff time, the access Request is then sent via a Request To Send (RTS) packet, where the RTS packet carries the source and destination address information.

Since the AP has no prior knowledge of the transmitting user, blind detection techniques are used to estimate the channel state information and decode multiple RTS packets simultaneously. Any other user that senses RTS will immediately freeze its backoff timer. In the illustrated embodiment, the RTS packet also includes information of the length of the data packet. When receiving an access request, the AP performs cross-layer resource allocation of subcarriers, bits, and power using information of channel and packet length. At the same time, the parameters of the space-time coded beamformer are also calculated. After the space within a short frame (SIFS), an access approval signal is then broadcast via a Clear To Send (CTS) packet To notify a specific user of the allocation result and channel information. The CTS packet provides space-time coded beamformer parameters instead of the actual channel gain. Once the user receives the CTS packet, the selected user waits for a SIFS interval and then starts transmitting a data packet. The orthogonal training sequences to be transmitted in the preamble of the data packet may be selected according to the order of the user addresses received in the CTS packet. When the data transmission is completed, the AP checks the received packet. An Acknowledgement (ACK) is then returned to the user to indicate that a successful data transmission occurred after the SIFS interval. When an RTS packet is received, channel state information for user assignment is estimated, which may become partially outdated for data transmission due to Doppler (Doppler) effects.

In the illustrated embodiment, if the number of users that synchronously transmit RTS packets does not exceed the number of receive antennas, it is assumed that the AP can successfully receive the RTS packets. Thus, the number of allowed users that can be supported synchronously, K, is no greater than M_r. In particular, the allowed users select the users with the smallest back-off time for those syncs. If a collision occurs (e.g., when the number of users that synchronously send RTS packets exceeds M)_rTime), the contention window is doubled for each retransmission until it reaches the maximum CW_max. In addition, if a packet error is detected, but also during an acknowledgement expiry period (ACT)_timeout) If no ACK is received, retransmission occurs. Resetting CW to CW when packet transmission is successful_min。

During RTS transmission, existing space-time coding is used at the transmitter, and therefore blind detection is employed at the AP receiving multiple RTS packets. When the RTS packet is successfully decoded, the AP can identify the sender and inform them of the orthogonal training sequences to be used during the data transmission phase. Channel state information is then estimated in the preamble of the data frame, from which information a multi-user detection technique can be employed at the receiver to separate the multiple data packets.

Exemplary transmitter and receiver configurations during data packet transmission are given in fig. 3 and 4, respectively. The frequency band is divided into N subcarriers. The serial data stream for user k is converted into multiple parallel branches by demultiplexing 302. To form a space-time coded OFDM block, two successive OFDM symbols are paired. The allocation result is sent as control information 306 from the AP to the receiver of the mobile user via a CTS packet. Depending on the number of bits and power allocated to each subcarrier, the adaptive modulator may use a corresponding QAM modulation scheme 304. A space-time coded beamformer 308 is then applied to each subcarrier. The resulting symbols may be converted to time domain samples by an Inverse Fast Fourier Transform (IFFT) 312. Next, a guard interval 314 is added and the samples are sent to the AP over a frequency selective fading channel via antenna 316.

At the receiver (e.g., AP), the guard interval 404 is removed and the samples are converted back to the frequency domain by the FFT block 406. From knowledge of the channels and the beamformers for space-time coding of different users, multi-user detection 408 is applied to suppress Multiple Access Interference (MAI) and jointly estimate the transmitted signals for all users. Multi-user detection is configured using subcarrier, bit and power allocation information 401.

Channel averaging feedback is concentrated where: wherein the spatially attenuated channel is modeled as a gaussian random variable with a non-zero mean and a white covariance adjusted based on channel feedback. The channel model may accommodate different types of partial channel state information, such as outdated channel state information due to feedback delay, and uncertain channel state information due to channel estimation, prediction, or feedback errors.

When the RTS packet is received, the channel state information is obtained, and in a certain embodiment, perfect estimation of the channel state information is assumed. However, due to the time difference between the RTS and the data packet at this time, such channel state information will be partially outdated compared to the actual channel information. Thus, in at least some embodiments, it is assumed that the channel information portion is out of date and the associated transmitter design is performed. Specifically, M is calculated for subcarrier n and user k_r×M_tThe MIMO channels are modeled as:

h [ n, k ] + xi [ n, k ] (equation 1)

Wherein, H [ n, k]For a given feedback information H^f[n，k]Is (H) n, k]Is averaged, andis related toThe connected zero mean value perturbs the matrix. Determine the pair (H [ n, k)]，σ_ε ²) Parameterizing partially outdated state information, variance σ_ε ²[n，k]Reflecting the quality of the channel state information. Finite Impulse Response (FIR) channel between different transmit and receive antenna pairsIndependently of each other, and h_μv[k]L branches { h } of_μv[l，k]}_l＝1 ^LWhen not relevant:

and

(equation 2)

Where ξ denotes the correlation coefficient between the actual channel and the estimated channel in the time domain, and σ denotes_h ^zThe total energy of all FIR channels for all allowed users. When considering the Doppler effect, ξ depends on the time difference t_ΔNormalized Doppler frequency f_d. I.e. xi ═ J₀(2πf_dt_Δ) Wherein, J₀(. cndot.) is a first class of zeroth order Bessel (Bessel) function.

Generally, in an 802.11 based wireless network in infrastructure mode, there is no exchange of information between different users. Thus, each user independently designs the space-time coded beamformer from its own channel, regardless of the other mobile to AP links. A space-time coded beamformer is configured for each user's transmitter. Since the transmitter configuration is similar for all users and subcarriers, only a single user k and subcarrier n will be discussed below. However, it will be appreciated that there are actually multiple users and multiple subcarriers. For the following discussion, the brackets [ n, k ] are not discussed again for the sake of brevity.

The structure of the space-time coded beamformer is depicted in fig. 5. Using modulated symbols s₁And s₂An Alamouti spatio-temporal matrix is generated. However, it will be recognized that other space-time block coding schemes may be used in other embodiments. Using the percentage delta₁、δ₂Splitting the transmit power produces a delta for the first base beam₁P and δ for the second base beam₂And P. Then, the symbols loaded with power are multiplied by two beamforming vectors respectivelyAndcan adjust the variable (v)₁，v₂，δ₁，δ₂) To optimize average Bit Error Rate (BER) performance. Let d²Represents the proportional squared Euclidean (Euclidean) distance of the constellation as a function of the power loading P and the number of loaded bits b. Next, the threshold d will be used₀ ²Obtaining a target BER_t。

Multiple users may transmit on the same subcarrier and may separate overlapping symbols at the receiver using multiple antenna techniques. For each subcarrier, the receiver (e.g., AP) aims to estimate the modulated symbols sent from different users. The subcarrier allocation information is then used to identify the corresponding user allocated to that subcarrier. Using the transmitter design, the hierarchy can be viewed as a space-time block coded (STBC) system where each symbol is transmitted through a beam. Thus, the multi-user detection Method (MUD) originally designed for multi-user STBC systems can be applied to jointly detect transmitted signals for different users. In one embodiment, Maximum Likelihood (ML) multi-user detection is used, which may be the best reception architecture that maximizes a posteriori probability. It will be appreciated that other types of MUD, such as Zero Forcing (ZF), Minimum Mean Square Error (MMSE), Parallel Interference Cancellation (PIC), and Successive Interference Cancellation (SIC), may also be deployed at the receiver with less complexity.

As mentioned previously, the challenges faced behind SDMA and the presence of co-channel interference (CCI) make it difficult to solve the resource allocation problem. To deal with these problems, a grouping method is used which divides all users into several groups, so that it is expected to ensure low interference between any pair of users from different groups.

A cross-layer approach to maximizing system throughput has been developed. To achieve this, the best user combination may be selected from all allowable combinations for each subcarrier, and bits and power are allocated according to partially outdated channel state information. The impact of user separation is examined according to an allocation policy. Such allocation policies are intended to indicate conditions that allow users to share the same subcarriers. The resource allocation problem can then be formulated taking into account both medium access control problems and physical layer problems.

Allocation in a MIMO/OFDM system involves selecting users on each subcarrier, and bit and power allocation for each user. A good allocation strategy should be able to prevent users with low degrees of separation from being allocated to the same sub-carriers, since the resulting high interference will significantly reduce the system capacity. To achieve this and to make the allocation problem traceable, the user allocation is dynamically controlled according to the degree of separation of the users, so that mutual interference can be significantly avoided. The degree of separation of the users can be determined based on the correlation of the channel matrix between the users. However, partially outdated channel state information is available. Thus, the correlation for different channels and the performance of different channel feedback qualities can be examined.

Let user k₁，k₂Of the channel matrixThe decomposition is as follows:

and(equation 3)

In case of good channel state information, the space-time coded beamformer is reduced to the existing beamformer. Thus, the receive antenna weight vectorAndis equal toAndthe first column vector of (1). By

(equation 4)

Channel correlations dependent on the receive antenna weight vectors are defined.

Next, a condition is defined according to which users can be allocated to the same subcarrier without interfering with each other. The influence of p defined by equation 4 is examined.

Figure 6 represents the performance of an ML multi-user detection receiver as a function of p at different values of the channel feedback quality ξ as defined in equation 2. Fig. 6 illustrates curves for single user range and MLD at 1(605, 610), 0.8(615, 620), and 0.6(625, 630), respectively. As ξ decreases, the single-user Bit Error Rate (BER) range increases. On the other hand, the value of ρ has an important influence on the BER performance. Also, as ξ decreases, the range of ρ in which the BER using the multi-user detection technique is very close to the single-user range becomes smaller. However, the BER curve becomes smoother. Thus, to determine whether users can be assigned to the same subcarrier, both the value of ξ and the value of ρ may be considered. Xi (xi)_thAnd ρ_thTwo thresholds are indicated. If xi > xi_thAnd ρ < ρ_thThen both users are allowed to be on the same subcarrier. Thus, given outdated channel information, when the channel feedback quality ξ is low, the correlation of the actual channel is not guaranteed.

When the allocation of the subcarriers is controlled so that the correlation between each pair of users is below a threshold p_thWhen the temperature of the water is higher than the set temperature,a wireless network system may be considered to be interference free. Determining ρ from channel feedback quality ξ and a multi-user detection architecture used at the receiver_thThe value of (c). Thus, the allowability of each user combination may be defined. Each combination corresponds to a subset of users. Here, there is a total of 2^kA possible combination. For example, assume that K ═ 4. A total of 16 combinations from (0, 0, 0, 0) to (1, 1, 1, 1) can be obtained. Each combination corresponds to a set of users, where a value of 1 or 0 indicates whether the respective user is an element in such a set. If the combination is in the corresponding subset of users, the combination is allowable and higher than ρ cannot be used_thThe correlations of (2) find user pairs. The channel feedback quality ξ is an indirect parameter for checking the allowable combinations and is in determining ρ_thPlay a role in the course of the value of (c). Specifically, the handle 1_i，nDefined as the admissibility index of the ith combination on the nth subcarrier. That is to say that the first and second electrodes,

(equation 5)

For example, consider ρ_th0.5 for 4 users. If the correlation matrix n on the subcarrier consists of

(equation 6)

Given, then 1_6，nThis means that a 6 th combination (0, 1, 0, 1) representing a set comprising user 2 and user 4 is allowable. Also, 1_12，n0 means that the combination (1, 0, 1, 1) is not allowable because user 1 and user 4 cannot be allocated to the same subcarrier.

The allocation is determined taking into account all allowable user combinations. Assume that the AP successfully receives RTS packets from K users. The goal may be to allocate subcarriers, bits, and power so that data packets may be sent within a minimum delivery time (airtime). In general, minimizing transmission time is equivalent to maximizing data rate. From the physical layer perspective, at a given QoS requirement and total power constraint P_totalIn this case, a target may be set to maximize the total data rate. However, this may not be the case if problems in upper layers of the network stack are considered. For example, different users may have packets with different lengths, which are determined by the characteristics of the application. The data transmission time is governed by the users using the maximum number of OFDM symbols. In such a case, maximizing the total data rate does not reduce the minimum delivery time. Therefore, additional constraints are added such that the allocated data rate in each OFDM symbol is proportional to the user's packet length. Mathematically, then, the optimization problem can be solved as follows:

(equation 7A)

The following equation is conditional:

(equation 7B)

(equation 7C)

(equation 7D)

To limit interference to other Basic Service Sets (BSSs) or neighboring systems and to compare different schemes under the same transmission power condition, the total power constraint is given by equation 7B. However, it will be appreciated that in the allocation technique, the situation of individual power constraints can be easily extended by applying similar techniques. In the above equation, β_i，nRepresents the packet length of user k and is defined as:

(equation 8)

In order for the problem to be traceable,can refer to beta in equation 7A_i，nRelaxed to the interval [0, 1 ]]Real number in (2). Can convert the real value of beta_i，nInterpreted as the time sharing factor of the ith combination on the nth subcarrier. Specifically, if the number of OFDM symbols for transmitting a data frame is N_sThen at N_sβ_i，nDuring each OFDM symbol, the ith combination is allocated to the nth subcarrier. For example, consider 4 users and a first subcarrier. The data frame includes N_s40 OFDM symbols. Moreover, if the 4 th combination ((0, 0, 1, 1) including user 3 and user 4) and the 13 th combination ((1, 1, 0, 0) including user 1 and user 2) share the same beta_4，10.4 and beta_13，1User 3 and user 4 will occupy this subcarrier of the first 16 OFDM symbols, while user 1 and user 2 will share the subcarriers of the remaining 24 OFDM symbols. On the other hand, f_k，i，n(P_k，i，n) For at a given allocated power P_k，i，nThe rate function of the ith combined user k on subcarrier n. Assume that adaptive M-QAM is used, and then BER is given a target bit error rate_iAnd transmit power P, the number of bits that can be transmitted in each symbol is approximated as:

(equation 9)

Wherein d is calculated in such a way₀ ²：

Wherein the content of the first and second substances,

or, if no delta is found₂D > 0₀ ²：

For the sake of brevity, let

(equation 10)

For a particular user k and subcarrier n, y_k，nRepresenting equivalent channel conditions. Then, a rate function f is obtained_k，i，，n(P_k，i，，n) Comprises the following steps:

(equation 11)

Wherein phi_iRepresenting a set of users included in the ith combination. 1_i，，nAnd f_k，i，，n(P_k，i，，n) Both depending on the transmitter and receiver configuration.

The constraints in equation 7D include (K-1) independent equations. Alternatively, this constraint can also be replaced by K related inequalities, since if a is₁≤a₂≤…≤a_k≤a₁Can obtain a₁＝a₂＝…＝a_k＝a₁. That is to say that the first and second electrodes,

(equation 12)

Here, [. C]_KRepresents a modulus based on K, wherein 1 ≦ g [. cndot.]_K… is less than or equal to K. For example, [ -1 [ ]]_K＝K-1、[0]_KK, and [ K +1 ═ K]_K＝1。

f_k，i，n(P_k，i，n) Is a concave function. However, in (. beta.)_i，n，P_k，i，n) In equation 7A, the objective function β_i，nf_k，i，n(P_k，i，n) Not concave. Therefore, if c_k，i，n＝β_i，nThen equations 7A-7D can be rewritten as:

(equation 13A)

The following equation is conditional:

(equation 13B)

(equation 13C)

(equation 13D)

At beta_i，n∈[0，1]And c is_k，i，nBeta is greater than or equal to 0_i，nf_k，i，n(c_k，i，n/β_i，n) Is concave. On the other hand, 1_i，nThe concavity of the objective function is not changed. The lagrange (Lagrangian) quantity is obtained:

(equation 14)

Wherein, λ and t_nLagrange multipliers, u, for equations 13B and 13C_kIs the Karush-Kuhn-Tucker (KKT) multiplier of equation 13D. Thus, an optimal solution (c) can be obtained_k，i，n ^*，β_i，n ^*) The KKT conditions of (a) are combined as follows:

if it is not

(equation 15A)

And

(equation 15B)

Otherwise, ifThen it is determined that,

for allAnd c is_k，i，n＞0，(equation 15C)

In addition, other KKT conditions include

(equation 15D)

u_kK ≧ 0, K ═ 1,.., K, (equation 15E)

And the constraints expressed in equations 13B to 13D.

When 1 is_i，，nWhen the content is equal to 0, the content,

and(equation 16)

When 1 is_i，nWhen 1, equations 15A and 15C are used

(equation 17)

Wherein

(equation 18)

On the other hand, from equations 15B and 15C

(equation 19)

Wherein

(equation 20)

And

(equation 21)

In order to satisfy the constraint of equation 13C,

and isFor all i ≠ i' (Eq. 22)

Wherein

(equation 23)

Here, Ψ_nRepresenting the set of allowable combinations in the nth subcarrier.

Given (λ, u)₁，u₂，…，u_k) Can obtain (C)_k，i，n ^*，β_i，n ^*) The optimal solution of (1). However, to satisfy the KKT condition of equations 13B, 13D, 15D, and 15E, the pair (λ, u)₁，u₂，…，u_k) The value of (c) is adjusted.

As a result of this, the number of the,an iterative technique according to one embodiment yields (λ, u) as follows₁，u₂，…，u_k) The value of (c):

step 1: initializing KKT multiplier u₁＝u₂＝…u_k0 and λ is initialized to a minimum value.

Step 2: according to (lambda, u)₁，u₂，…，u_k) Is calculated using equations 16-23 (C)_k，i，n ^*，β_i，n ^*) To a temporary optimal solution.

And step 3: it is checked whether the KKT condition based on equation 13B is satisfied. If so, go to the next step. If not, the value of λ is adjusted and step 2 is repeated using the updated value of λ until the total power constraint in equation 13B is satisfied.

And 4, step 4: it is checked whether the KKT conditions based on equations 13D, 15D, and 15E are all satisfied. And if so, stopping.

Iteratively searching if one or more conditions are not satisfied (u)₁，u₂，…，u_k) The value of (c).

In each iteration, a user k is selected that satisfies the following equation^o：

(equation 24)

Wherein the content of the first and second substances,

(equation 25)

And

(equation 26)

To make it possible toSearching using a bisection methodThe value of (c). Specifically, the initial low rangeSet to the current valueAnd setting the initial high range to:

(equation 27)

Wherein the content of the first and second substances,this means for user k in all subcarriers^oThe optimum channel gain.

For initial high rangeThe arrangement is made such that for all n,in such a case, it is preferable that,thus, lead toIs/are as followsShould be at the correct value ofAndin the meantime.

Order toAnd useAnd (5) repeating the step (2).

If it is notOrder to

(equation 28)

Otherwise, ifOrder to

(equation 29)

Repeating the halving search process until

According to equation 24, go to another user, and repeat the iterative process until all KKT conditions in equations 13D, 15D, and 15E are met.

And 5: and repeating the step 3 and the step 4.

When the condition is not found to be satisfiedIs/are as followsWhen the value of (3) is greater than the value of (3), the halving search process of step (4) is performed. Next, the search process may beAndoscillating between the two cases, since the two combinations may alternately occupy the same subcarrier. Thus, at a given pointIn the case of the critical value of (c), the two combinations have the same value of G on that subcarrier (see equation 20). In such a case, a sharing factor β may be used_i，nTake the values in interval (0, 1). In particular, it is assumed that there is a shared same subcarrier n^oTwo combinations of i₁And i₂. If only combination i is selected₁Then will target user k^oAnd user [ k ]^o+1]_KThe resulting total ratio per OFDM symbol is expressed asAndalternatively, if only combination i is selected₂The resulting total ratio per OFDM symbol is changed toAnd

then, the following sharing factor for the two combinations can be obtained:

(equation 30)

And

(equation 31)

An OFDM system is simulated with 64 sub-carriers over a 20MHz frequency band. The wireless channel is modeled as a 6-way Rayleigh fading channel with an exponential power delay pattern and a Root Mean Square (RMS) delay spread of 300 ns. In this simulation, assume the number of transmit antennas equipped at each mobile device, M_tEqual to 2, and number of receive antennas M at each AP_rEqual to 4. Selection 10^-6Target BER of_tTo maintain a low probability of packet errors and retransmissions. The feedback quality ξ (as defined in equation 2) is typically 0.8 or above 0.8, as determined by normalization to the Doppler frequency. Thus, for the purposes of the simulation, it is assumed that ξ is 0.8 (f) at the emitter_dt_Δ0.15) and p is set accordingly_th0.4. Also, the packet length (including payload and media access control header) is evenly distributed between 100 bytes and 1000 bytes.

In fig. 7, the average number of OFDM symbols per packet is illustrated for a cross-layer scheme over two other schemes. In particular, fig. 7 illustrates curves for a cross-layer method 730, physical layer optimization 720, and fixed allocation 710. A situation with 4 users is simulated. The first scheme for comparison is one in which: the original data rate is maximized from the physical layer perspective, but the problem of the packets in the upper layer is not considered (e.g., there is no constraint of equation 7D resulting from the original problem). This scheme is referred to as physical layer optimization. The second scheme, referred to as fixed allocation, employs Frequency Division Multiple Access (FDMA)) And fixed modulation based on existing beamforming. By making delta₁1 and δ₂As 0, existing beamforming can be obtained. On the other hand, the number of OFDM symbols per packet is defined as the number of OFDM symbols used for data transmission divided by the number of packets included in the data frame.

As mentioned above, the duration of each data frame is determined by the user. Consider the case of 4 users. Defining the transmitted signal-to-noise ratio (SNR) per subcarrier as SNR P_Total/(N·N₀) Wherein N is₀Representing the noise power. Without loss of generality, N is in this simulation₀1. It can be easily seen from the figure that the number of OFDM symbols used by the cross-layer method is significantly less than the number of the other two schemes over the entire range of SNR considered. Therefore, the cross-layer method can always achieve an improvement in throughput and can utilize resources more efficiently. Using fixed allocation or physical layer optimization, the number of OFDM symbols used can increase to infinity in low SNR regions, since fixed allocation is typically inefficient, which may result in zero allocation with low total power budget. In the case of physical layer optimization, some users with poor channel conditions may be cut off to maximize the sum of the data rates of all users. Therefore, these switched off users dominate the number of OFDM symbols and will tend to approach infinity. Thus, optimization in a single layer may not be efficient. In contrast, the cross-layer approach has many advantages.

The throughput performance of the different schemes will be examined by simulation and/or experiment. For the purposes of these simulations/experiments, it was assumed that the Rayleigh attenuation was quasi-stationary in each data frame and independent from each other between different data frames. Using a filter with 20K_tA system of individual users, and the maximum number of users that can be supported synchronously is K_max＝M_r4. It is also assumed that the traffic is saturated traffic. In the compensation process, CW_minEqual to 8, and CW_maxEqual to 256.

In one embodiment, the format of the control frame, including RTS, CTS, ACK, is designed according to the current 802.11a standard, and consists of a frame control field (2 bytes), a duration field (2 bytes), a Receiver Address (RA) field (6 bytes), a Transmitter Address (TA) field (6 bytes, only in RTS), and a frame check sequence (FCS, 4 bytes). However, it will be appreciated that other formats for control frames may also be used. Since MPR is supported, multiple RA fields may be required for CTS and ACK frames to acknowledge nodes with successful RTS requests or data transmissions. All control frames may be transmitted at the same rate (e.g., 6Mbps) or at a variable rate. Other parameters used in the simulation are listed in table 1. However, it will be recognized that these parameters are merely exemplary, and in other embodiments, other parameter values may be used.

Table 1:

time slot	9us
		SIFS	16us
DIFS	34us
		PHY header	20us
OFDM symbol duration	4us
		CTStimeout	300us
ACKtimeout	300us

In contrast to the cross-layer approach where MPR and adaptive resource allocation are designed in combination, neither MPR nor adaptive resource allocation is applied in classical wireless systems. These previous methods are referred to as MPR + Fixed Resource Allocation (FRA), MPR + no Dynamic Resource Allocation (DRA), and MPR + no FRA, respectively. Another scheme for comparison is one in which: where the AP detects multiple RTS packets but sends CTS to one user using adaptive resource allocation only. This scheme is referred to as multiple RTS reception (MRSD) with a single data packet transmission. Fig. 8 shows the average throughput achieved by the different techniques when the SNR increases from 5dB to 30 dB. In particular, fig. 8 illustrates plots of a cross-layer method 810, MPR + FRA 820, MRSD 830, no MPR + DRA 840, and no MPR + FRA 850. A data packet is defined as being successfully received if all of the bits in the data packet are correctly decoded.

The average throughput is then defined as the average number of packets successfully received over a unit of time (e.g., ms). For this simulation, an uncoded system was assumed. The cross-layer approach can achieve significant improvement in average throughput compared to other schemes. Also, MPR + FRA outperforms MRSD and MPR + DRA-free in performance in most cases except in the low SNR range. Thus, MPR plays a more important role than DRA as the SNR increases, since the overhead required for channel access contention can be significantly reduced by scheduling multiple users at once. Careful observation of the figure further shows that the average throughput for the non-MPR scheme appears to be more stable for different SNRs than the scheme using MPR. On the other hand, in the high SNR range, the throughput difference between the w/o MPR + DRA and w/o MPR + FRA schemes becomes narrow.

In the above experiment, the sample with 20K was used_tA system of individual users. Simulations were performed to determine the performance of the scheme at different network scales. Figure 9 compares the average throughput of different schemes when the number of users in the network increases from 5 to 100. The SNR was assumed to be 15dB for this simulation. Fig. 9 illustrates plots of cross-layer method 910, MPR + FRA 920, MRSD 930, no MPR + DRA 940, and no MPR + FRA 950. The cross-layer approach outperforms the other schemes in performance, both for small-scale systems and for large-scale systems. In addition, the MPR + FRA-free method also has very similar performance to the MPR + DRA-free method, with the number of users K_tIs increased, it decreases monotonically. In particular, with these schemes, as the number of competing access users increases, more conflicts occur and, therefore, more resources are wasted.

In contrast, with the minimum network size, the peak throughput of the cross-layer method or the MPR + FRA scheme cannot be achieved. In particular, from K is described_t5 to K_tThe throughput increase using the cross-layer method is 30 because resources are efficiently utilized and multi-user diversity cannot be fully utilized when the number of users is relatively small. Therefore, the number of users corresponding to the maximum throughput in the cross-layer method is greater than that of the MPR + FRA scheme. On the other hand, the throughput of the MRSD remains substantially unchanged with respect to the number of different users, because no multi-user diversity gain can be utilized, and the use of multiple RTS reception control can reduce collisions as the number of users increases.

In the experiments described so far, it was assumed that the traffic in the network was saturated. However, it is more practical to make a generalized assumption about the traffic arrival pattern. In this section, according to the parameter r_jA Poisson distribution of (i) generates a packet for a queue of user j. The time interval between the arrival of two successive packets then follows an exponential distribution. r is_jIs in unit time toStrength of arrival, or packet arrival rate. Suppose K_tThe packet arrival processing for each user is independent and the network capacity is represented by η. In particular, in order to stabilize or balance the system,should not be greater than η.

Fig. 10 illustrates the average packet delay for different packet arrival rates. The packet delay is defined as the time interval from the arrival of a packet until the reception of an ACK for the packet. Specifically, fig. 10 illustrates SNR 15dB and K_tPacket delay of 20. Fig. 10 illustrates plots of cross-layer method 1050, MPR + FRA 1040, MRSD 1030, no MPR + DRA 1020, and no MPR + FRA 1010. Without loss of generality, it is assumed that the packet arrival rate, denoted r, is the same for all users. With MPR + DRA, when r is greater than 0.18 packets/ms, the system becomes unstable (e.g., the average packet delay increases indefinitely over time). The performance of MRSD, MPR + DRA, and MPR + FRA is even worse, which results in infinite packet delay unless the packet arrival rate is lower than 0.15, 0.13, 0.12 packets/ms, respectively. In contrast, in the case of heavy traffic load, the average packet delay using the cross-layer approach is significantly lower than that of the other schemes. In particular, when packets arrive at a rate of 0.18 packets/ms, the technique may achieve a delay reduction of 60% compared to MPR + FRA. In addition, the system can remain stable as long as the packet arrival rate does not exceed 0.26 packets/ms. Also, from the results illustrated in fig. 8, it can be derived: the network capacity η using this technique is about 5.2 packets/ms at a SNR of 15 dB. Here, this validates the theory that: when the accumulated packet arrival rate K_tR is less than the network capacity η, the system is stable. On the other hand, as traffic load decreases, the packet delay gap between different schemes gradually shrinks and eventually disappears.

The average packet delay for these schemes is determined given different values of SNR. FIG. 11 illustrates a hypothetical packet arrival rater-0.14 packets/ms and K_tComparison of average packet delays at 20. Specifically, fig. 11 illustrates plots of a cross-layer approach 1150, MPR + FRA 1140, MRSD 1130, no MPR + DRA 1110, and no MPR + FRA 1120. As expected, the average packet delay decreases with increasing SNR, and the cross-layer approach is significantly better in performance than other schemes over the entire SNR range. In order to stabilize the system, the cross-layer approach may obtain SNR advantages of 5dB, 6dB, 11dB, 14dB compared to MPR + FRA, MRSD, MPR + DRA-free, and MPR + FRA-free, respectively. Also, it can be seen that, unlike fig. 9, for light traffic loads, the gap in packet delay is reduced, and even for high SNRs, the delay performance of the different schemes does not converge. The reason for this is that MPR can significantly reduce the probability of collisions and improve packet delay when the traffic load is not too high compared to the non-MPR scheme.

The throughput performance of the different schemes with different packet arrival rates is illustrated in fig. 12. In particular, fig. 12 illustrates plots of cross-layer method 1250, MPR + FRA 1240, MRSD 1230, no MPR + DRA 1220, and no MPR + FRA 1210. Each scheme has a threshold for packet arrival rate that has a significant impact on system throughput. When the packet arrival rate is below such a threshold, the throughput decreases linearly with increasing packet arrival rate. Otherwise, the throughput remains substantially unchanged. This phenomenon can be easily understood and these thresholds can be obtained from fig. 10, at which point the system becomes unstable and the packet delay tends to be infinite. Alternatively, these thresholds may be determined by dividing the network capacity (e.g., the maximum system throughput achieved in a saturated case) by the number of users.

Referring to fig. 13, an exemplary system at a receiver according to one embodiment is illustrated. In this example, the receiver has multiple receive antennas 1380 and multiple transmit antennas. The system has various components that can be implemented in hardware or software. In the illustrated system, there are 5 components: a Request To Send (Request To Send) section 1310, a transmission parameter section 1320, a Clear To Send (Clear To Send) section 1330, a data receiving section 1340, and a wide area network access section 1350.

Request transmission section 1310 receives a request transmission packet from a publisher, the packet including channel state information. Transmission parameters component 1320 determines transmission parameters that minimize delivery time based at least in part on channel state information provided in the request transmission. The transmission permission section 1330 generates a transmission permission packet having the determined transmission parameter and transmits it to the transmitter that made the request transmission. The data receiving section decodes the data received from the plurality of transmitters using the transmission parameters. Some of the decoded data may be transmitted via wide area network access component 1350 for delivery to a wide area network, such as the internet.

With respect to the exemplary systems described above, various methods that can be implemented in accordance with the disclosed subject matter will be better appreciated with reference to the flowcharts of fig. 14 and 15. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of blocks, it is to be appreciated that the claimed subject matter is not limited by the order of the blocks, as some blocks may occur in different orders and/or concurrently with other blocks from what is depicted and described herein. Where non-sequential (i.e., branch) flow is illustrated by flowcharts, it will be appreciated that various other branches, flow paths, and orders of the modules may be implemented which achieve the same or similar result. Moreover, not all illustrated blocks may be required to implement the methodologies described hereinafter.

Referring to fig. 14, a method 1400 of a user equipment transmitter is illustrated. At 1405, the channel is sensed to determine whether the channel is free. When the channel is idle 1410, at 1415, the transmitter waits a random time that does not exceed the contention period. It will be appreciated that the random time may be a pseudo-random time. At 1420, a Request To Send (RTS) frame is sent to the receiver. The frame includes address information and channel state information. If a conflict occurs, the contention period is doubled and acts 1415 and 1420 are repeated. Finally, at 1430, a clear to send frame is received from the receiver with the transmission parameters. At 1440, data is transmitted according to the transmission parameters. At 1445, the method may continue to allow for the transmission of more data.

Referring to fig. 15, a method 1500 of a receiver is illustrated. For the sake of brevity, the method is described for the case of communicating with a single transmitter. However, it will be recognized that the receiver may interact with multiple transmitters simultaneously.

At 1505, a Request To Send (RTS) frame is received. The RTS packet includes channel state information as well as address information. At 1510, the transmitter is identified, e.g., using address information in the RTS packet. At 1515, an Acknowledgement (ACK) is sent to the identified transmitter. At 1520, transmission parameters are determined to make efficient use of the physical layer, e.g., by performing steps 1-5 above. At 1525, a Clear To Send (CTS) frame is sent with the determined transmission parameters. At 1530, data is received from the transmitter.

Exemplary user equipment

As mentioned above, the invention applies to any device in which it may be desirable to function as a receiver or transmitter in a wireless network, where the receiver or transmitter has multiple antennas. It should be appreciated, therefore, that handheld, portable, and other computing devices and computing objects of various types are contemplated for use in connection with the present invention, i.e., where any wireless device is available to receive, process, or store data. Thus, the generic user equipment described below in FIG. 16 is but one example, and the present invention may be implemented using virtually any computing device having wireless network interoperability and interaction capabilities.

Thus, FIG. 16 illustrates an example of a suitable computing system environment 1600 in which the invention may be implemented, although as made clear above, the computing system environment 1600 is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment 1600 be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment 1600.

With reference to fig. 16, an exemplary remote device for implementing the present invention is illustrated, which includes a user device 1610 in the form of a computer. Components of computer 1610 may include, but are not limited to, a processing unit 1620, a system memory 1630, and a system bus 1621 that couples various system components including the system memory to the processing unit 1620. The system bus 1621 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures.

Computer 1610 typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer 1610. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media may include volatile and nonvolatile, removable and non-removable media implemented in a method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CDROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by computer 1610. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media.

The system memory 1630 may include computer storage media in the form of volatile and/or nonvolatile memory such as Read Only Memory (ROM) and/or Random Access Memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the computer 1610, such as during start-up, may be stored in memory 1630. Memory 1630 typically also includes data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit 1620. For example, and not by way of limitation, memory 1630 may also include an operating system, application programs, other program modules, and program data.

The computer 1610 may also include other removable/non-removable, volatile/nonvolatile computer storage media. For example, computer 1610 may include a hard disk drive that reads from or writes to non-removable, nonvolatile magnetic media; a disk drive that reads from or writes to a removable, nonvolatile disk; and/or an optical disk drive that reads from or writes to a removable, nonvolatile optical disk such as a CD-ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. A hard disk drive is typically connected to the system bus 1621 through a non-removable memory interface such as an interface, and a magnetic disk drive or optical disk drive is typically connected to the system bus 1621 by a removable memory interface, such as an interface.

A user can enter commands and information into the computer 1610 through input devices such as a keyboard and pointing device, commonly referred to as a mouse, trackball or touch pad. Other input devices may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit 1620 through a user input device 1640 and one or more associated interfaces coupled to the system bus 1621, but may be connected to the processing unit 1620 by other interface and bus structures, such as a parallel port, game port or a Universal Serial Bus (USB). A graphics subsystem may also be connected to system bus 1621. A monitor or other type of display device is also connected to the system bus 1621 via an interface, such as output interface 1650, which in turn may communicate with video memory. In addition to a monitor, computers can also include other external output devices such as speakers and a printer, which may be connected through output interface 1650.

Computer 1610 may operate in a distributed environment using logical connections to one or more other remote computers, such as a remote computer 1670, which remote computer 1670 may have different capabilities than device 1610. The remote computer 1670 may be a personal computer, a server, a router, a network PC, a peer device or other common network node, or any other remote media consumption or transmission device, and may include any or all of the elements described above relative to the computer 1610. The logical connections depicted in FIG. 16 include a network 1671, such a wireless Local Area Network (LAN), but may also include other networks/buses.

The computer 1610 is connected to the wireless LAN 1671 through a network interface or adapter having multiple antennas. When used in a WAN networking environment, the computer 1610 typically includes a communication component, such as a modem, or other mechanism for establishing communications over the WAN, such as the Internet. A communications component, which may be internal or external, such as a modem, may be connected to the system bus 1621 via the user input interface of the input device 1640, or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer 1610, or portions thereof, are stored in the remote memory storage device.

The methods and apparatus of the present invention may also be practiced via communications embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission, wherein, when the program code is received, it is loaded onto and executed by an apparatus, such as an EPROM, a gate array, a programmable logic device (PLA), a client computer, or the like, which becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates to invoke the functionality of the present invention. Additionally, any storage techniques used in connection with the present invention should necessarily be combined in hardware and software.

Furthermore, the disclosed subject matter may also be implemented as a system, method, apparatus, or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof to control a computer or processor based device that implements aspects described in detail herein. The term "article of manufacture" (also can be referred to as a "computer program product") as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., Compact Disks (CDs), Digital Versatile Disks (DVDs)), smart cards, and flash memory devices (e.g., memory cards, memory sticks). In addition, it is well known that carrier waves can be used to carry computer-readable electronic data such as those used in transmitting and receiving electronic mail or in accessing networks such as the internet or Local Area Networks (LANs).

The above-mentioned system has been described with respect to interaction between various components. It will be recognized that such systems and components may include the components or particular sub-components, some particular components or sub-components, and others, and in various permutations and combinations thereof as described above. Sub-components may also be implemented as components communicatively coupled to other components rather than included in parent components. Additionally, it should be noted that one or more components may be combined into a single component providing aggregate functionality or divided into multiple separate sub-components, and any one or more middle layers, such as a management layer, may be provided to communicatively couple to such sub-components so that integrated functionality may be provided. Any components described herein may also interact with one or more other components not specifically described herein but generally known by those of skill in the art.

While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom.

Although exemplary embodiments utilize the present invention in a particular network system environment, such as IEEE 802.11-like, the present invention is not so limited and virtually any wireless network may be used to provide a method for multi-packet reception medium access control and resource allocation. In particular, the techniques may be used in wireless networks of various sizes, such as wireless personal area networks, wireless metropolitan area networks, and wireless wide area networks. In addition, the present invention may also be implemented in or across a plurality of processing chips or devices. Therefore, the present invention is not limited to any single embodiment, but rather should be construed in breadth and scope in accordance with the appended claims.

The claims (modification according to treaty clause 19)

1. A computer-readable medium that performs a method for transmitting data in a multi-packet reception wireless network, the method comprising:

sensing a channel to determine if there are any pending transmissions in the multi-packet receiving network;

when the channel is idle for an interval exceeding a first predetermined time,

waiting a random time not exceeding a predetermined initial contention window;

sending a request sending control frame;

when a transmission permission control frame is received from the receiver,

waiting for a second predetermined time; and

transmitting data according to parameters specified in a clear to send control frame, wherein the parameters specified in the clear to send control frame are based on at least one of data associated with a channel state, or a length of at least one packet.

2. The computer-readable medium of claim 1, wherein transmitting data according to parameters specified in the clear to transmit frame comprises transmitting data by forming space-time coded OFDM blocks formed by pairing two consecutive OFDM symbols specified as part of the parameters.

3. The computer-readable medium of claim 1, wherein the method further comprises: when a collision occurs while the request transmission is made,

doubling the contention window;

waiting for a time when the channel is idle for more than a first predetermined time;

waiting for a random time not exceeding the one-time expanded contention window; and

the transmission request transmits a control frame.

4. The computer-readable medium of claim 3, wherein the method further comprises resetting the contention window to the initial contention window when the request to send control frame is successfully transmitted.

5. The computer-readable medium of claim 1, wherein the method further comprises re-transmitting the request to send the control frame if an acknowledgement is not received from the receiver within an acknowledgement expiration period.

6. The computer-readable medium of claim 1, wherein the wireless network is at least one of a wireless local area network and a MIMO wireless network.

7. The computer readable medium of claim 1, wherein the receiver is a wireless access point having a plurality of receive antennas.

8. A method of facilitating efficient use of a physical layer in a multi-packet reception wireless network, the method comprising:

for each of a plurality of request to send frames received at a receiver via one of a plurality of receive antennas:

identifying a transmitter associated with the request to send;

sending an acknowledgement back to the identified transmitter;

determining a set of transmission parameters based on at least one of a set of data associated with a channel status included in the request to send frame or a length of at least one packet, wherein the parameters include at least one of subcarrier information, bit information, or power information; and

transmitting a clear-to-send frame to the indicated transmitter with the determined set of transmission parameters.

9. The method of claim 8, wherein transmitting the clear to transmit frame with the determined transmission parameters comprises transmitting the clear to transmit frame with an OFDM block used in transmission.

10. The method of claim 8, wherein transmitting the clear to transmit frame with the determined transmission parameters comprises transmitting the clear to transmit frame with subcarrier, bit, and power allocation information.

11. The method of claim 8, wherein the receiver is a wireless access point.

12. The method of claim 8, wherein the wireless network is a MIMO wireless local area network.

13. The method of claim 8, wherein the determining transmission parameters to efficiently use the physical layer of multi-packet reception comprises determining subcarrier, bit, and power allocation information to reduce an amount of time to deliver for data transmission.

14. The method of claim 8, wherein the emitter is a SIMO device.

15. The method of claim 8, further comprising:

receiving data transmitted from a plurality of transmitters; and

the data transmitted from each transmitter is decoded using the determined parameters.

16. A system for efficient use of a physical layer in a MIMO-based wireless local area network, the system comprising:

a plurality of receiving antennas;

a plurality of transmit antennas;

a request transmission part which receives a request transmission frame from a transmitter, the frame including channel state information;

a transmission parameter component that determines a transmission parameter to minimize a delivery time based at least in part on channel state information provided in a request to send, wherein the transmission parameter comprises at least one of subcarrier information, bit information, or power information; and

and a transmission permission section which generates a transmission permission frame with the determined transmission parameter and transmits it to the transmitter which makes the request transmission.

17. The system of claim 16, further comprising a plurality of user devices, each having a plurality of transmit antennas and acting as a transmitter to generate the request-to-send request.

18. The system of claim 16, wherein the plurality of receive antennas further comprises a data receiving component that decodes data based on the determined transmission parameters.

19. The system of claim 18, wherein the plurality of receive antennas further comprises a wide area network access component that communicates the decoded data to a wide area network.

20. The system of claim 16, wherein the transmission parameters include subcarriers, bits, and power allocation information.

Statement or declaration (modification according to treaty clause 19)

Description of the invention

The following accompanying text is a modification of article 19 of the PCT treaty

The international bureau received a claim amendment from the related claims posted on date 06, 11/2009.

19 modifications and declarations in reply to the 2009 9/8 th international search report

Substitute sheets conforming to PCT treaty clause 19 (clause 46) and clause 28 are appended. Claims 1, 8 and 16 are amended. The comments herein are considered to honestly request an advantageous opinion of the present patent application.

Statement under treaty 19(1)

Claims 1, 8 and 16 are modified to further clarify that a set of transmission parameters may be determined by an access point (or other receiver) based at least in part on channel information and/or the length of a packet. Additionally, the transmission parameters may include subcarrier, bit, and/or power information and may be transmitted with a Clear To Send (CTS) message.

Claims 1-20 are true considering D1-US2007/007812, D2-Park et al, and D3-huntziker et al.

The present application relates generally to cross-layer multi-packet reception medium access control and resource allocation techniques for wireless networks having receivers with multiple antennas. A user device on a wireless network accesses the network for data transmission by making a Request To Send (RTS) request after a random backoff time. In response to a request to send, the access point (or other receiver) determines transmission parameters that optimize the use of the physical layer based on channel information and/or packet length, e.g., the parameters may include subcarrier, bit, and power allocation information. The transmission parameters are transmitted from the receiver to the indicated transmitter along with a Clear To Send (CTS) message. Upon receiving the CTS message, data is transmitted according to the transmission parameters.

In contrast, D1 discloses a technique for upgrading from a first multiple-input multiple-output (MIMO) wireless communication format to a second MIMO format in a wireless device communicating with a plurality of stations. Once an access point is upgraded to a new MIMO standard, a set of rules can be employed to elicit some response from a given station, thereby protecting stations that have not been upgraded (see [0056] - [0062 ]).

D2 relates to analyzing the efficiency of the ieee802.11n MAC protocol when it is used for a PHY rate of 1Gbps and, in addition, to examining in detail the effect of the MAC payload on that efficiency (see abstract and slides 3-5). However, D2 does not teach or suggest including a set of transmission parameters and a Clear To Send (CTS) message based at least in part on channel information included with the Request To Send (RTS) message.

D3 relates to an incorporated medium access and beamforming scheme for a packet-oriented, array antenna enhanced ad hoc network with time division multiplexing. The technique relates to enhancing the density of synchronous single-hop packet transmissions in a multipath fading environment (see abstract, part 3 and part 4).

However, unlike the claimed subject matter, none of the references D1, D2, and/or D3 disclose a user equipment requesting access to a data transmission on a network by waiting for a random backoff time and sending a request to send message at the expiration of the random backoff time. In addition, unlike the cited reference, the novelty of the present invention provides an access point or other receiver that determines a set of transmission parameters based on channel information included in a request-to-send message and sends the parameters along with an allow-to-send message.

Claims (20)

1. A computer-readable medium that performs a method for transmitting data in a multi-packet reception wireless network, the method comprising:

sensing a channel to determine if there are any pending transmissions in the multi-packet receiving network;

when the channel is idle for an interval exceeding a first predetermined time,

waiting a random time not exceeding a predetermined initial contention window;

sending a request sending control frame;

when a transmission permission control frame is received from the receiver,

waiting for a second predetermined time; and

data is transmitted according to parameters specified in the clear to send control frames.

2. The computer-readable medium of claim 1, wherein transmitting data according to parameters specified in the clear to transmit frame comprises transmitting data by forming space-time coded OFDM blocks formed by pairing two consecutive OFDM symbols specified as part of the parameters.

3. The computer-readable medium of claim 1, wherein the method further comprises: when a collision occurs while the request transmission is made,

doubling the contention window;

waiting for a time when the channel is idle for more than a first predetermined time;

waiting for a random time not exceeding the one-time expanded contention window; and

the transmission request transmits a control frame.

4. The computer-readable medium of claim 3, wherein the method further comprises resetting the contention window to the initial contention window when the request to send control frame is successfully transmitted.

5. The computer-readable medium of claim 1, wherein the method further comprises re-transmitting the request to send the control frame if an acknowledgement is not received from the receiver within an acknowledgement expiration period.

6. The computer-readable medium of claim 1, wherein the wireless network is at least one of a wireless local area network and a MIMO wireless network.

7. The computer readable medium of claim 1, wherein the receiver is a wireless access point having a plurality of receive antennas.

8. A method of facilitating efficient use of a physical layer in a multi-packet reception wireless network, the method comprising:

for each of a plurality of request to send frames received at a receiver via one of a plurality of receive antennas:

identifying a transmitter associated with the request to send;

sending an acknowledgement back to the identified transmitter;

determining transmission parameters to efficiently use a physical layer of multi-packet reception; and

transmitting a clear-to-send frame to the indicated transmitter with the determined transmission parameters.

9. The method of claim 8, wherein transmitting the clear to transmit frame with the determined transmission parameters comprises transmitting the clear to transmit frame with an OFDM block used in transmission.

10. The method of claim 8, wherein transmitting the clear to transmit frame with the determined transmission parameters comprises transmitting the clear to transmit frame with subcarrier, bit, and power allocation information.

11. The method of claim 8, wherein the receiver is a wireless access point.

12. The method of claim 8, wherein the wireless network is a MIMO wireless local area network.

13. The method of claim 8, wherein the determining transmission parameters to efficiently use the physical layer of multi-packet reception comprises determining subcarrier, bit, and power allocation information to reduce an amount of time to deliver for data transmission.

14. The method of claim 8, wherein the emitter is a SIMO device.

15. The method of claim 8, further comprising:

receiving data transmitted from a plurality of transmitters; and

the data transmitted from each transmitter is decoded using the determined parameters.

16. A system for efficient use of a physical layer in a MIMO-based wireless local area network, the system comprising:

a plurality of receiving antennas;

a plurality of transmit antennas;

a request transmission part which receives a request transmission frame from a transmitter, the frame including channel state information;

a transmission parameter component that determines a transmission parameter to minimize a delivery time based at least in part on channel state information provided in the request transmission; and

and a transmission permission section which generates a transmission permission frame with the determined transmission parameter and transmits it to the transmitter which makes the request transmission.

17. The system of claim 16, further comprising a plurality of user devices, each having a plurality of transmit antennas and acting as a transmitter to generate the request-to-send request.

18. The system of claim 16, wherein each receiver further comprises a data receiving component that decodes data transmitted to the receiver based on the determined transmission parameters.

19. The system of claim 18, wherein each receiver further comprises a wide area network access component that communicates the decoded data to a wide area network.

20. The system of claim 16, wherein the transmission parameters include subcarriers, bits, and power allocation information.