Name
Abstract | ||
|---|---|---|
This paper considers a simple on-off random multi- ple access channel, where n users communicate simultaneously to a single receiver over m degrees of freedom. Each user transmits with probability �, where typicallyn < m ≪ n, and the receiver must detect which users transmitted. We show that when the codebook has i.i.d. Gaussian entries, detecting which users transmitted is mathematically equivalent to a certain sparsity detection problem considered in compressed sensing. Using recent sparsity results, we derive upper and lower bounds on the capacities of these channels. We show that common sparsity de- tection algorithms, such as lasso and orthogonal matching pursuit (OMP), can be used as tractable multiuser detection schemes and have significantly better performance than single-user det ection. These methods do achieve some near-far resistance but—at high signal-to-noise ratios (SNRs)—may achieve capacities far below optimal maximum likelihood detection. We then present a new algorithm, called sequential OMP, that illustrates that iterative detection combined with power ordering or power shaping can significantly improve the high SNR performance. Sequential OMP is analogous to successive interference cancellation in the classic multiple access channel. Our results thereby provide insight into the roles of power control and multiuser detection on random-access signalling. The limits of on-off random access signaling with multiple users are not fully understood. To this end, we consider a simple random multiple access channel where n users transmit to a single receiver. Each user is assigned a single codeword which it transmits with probability λ. We wish to understand the capacity of these channels, by which we mean the total number of degrees of freedom m needed to reliably detect which users transmit as a function of n, λ, and the channel conditions. We also wish to establish performance bounds for specific decoding algorithms. |
Year | Venue | Keywords |
|---|---|---|
2009 | Clinical Orthopaedics and Related Research | orthogonal matching pursuit,maximum likelihood estimation,index terms— compressed sensing,convex optimization,mul- tiuser detection,multiple access channel,single-user detection,lasso,random matrices,power control,thresholding,sparsity,compressed sensing,information theory,maximum likelihood estimate,signal to noise ratio,upper and lower bounds,indexing terms,random access,degree of freedom |
Field | DocType | Volume |
Matching pursuit,Mathematical optimization,Upper and lower bounds,Power control,Single antenna interference cancellation,Multiuser detection,Compressed sensing,Mathematics,Random access,Codebook | Journal | abs/0903.1 |
Citations | PageRank | References |
32 | 1.99 | 25 |
Authors | ||
3 | ||
Name | Order | Citations | PageRank |
|---|---|---|---|
| Alyson K. Fletcher | 1 | 552 | 41.10 |
| Sundeep Rangan | 2 | 3101 | 163.90 |
| Vivek K. Goyal | 3 | 2031 | 171.16 |