Optimum asymptotic multiuser efficiency of randomly spread CDMA

  title={Optimum asymptotic multiuser efficiency of randomly spread CDMA},
  author={David Tse and Sergio Verd{\'u}},
  journal={IEEE Trans. Inf. Theory},
This correspondence analyzes the high signal-to-noise ratio (SNR) performance of optimum multiuser detectors for synchronous direct-sequence spread spectrum with random spreading in an additive white Gaussian noise channel. Under very general conditions on the received powers, we show that the optimum asymptotic efficiency of a K-user system with spreading gain N converges to 1 almost surely as K/spl rarr//spl infin/, and K/N is kept equal to an arbitrary nonzero constant. Therefore, the… 

Optimum Asymptotic Multiuser Efficiency of Pseudo-Orthogonal Randomly Spread CDMA

The high signal-to-noise ratio performance of the PO-CDMA is analyzed by rigorously deriving its asymptotic multiuser efficiency (AME) in the large system limit.

Asymptotic bounds on the Optimum Multiuser Efficiency of randomly spread CDMA

We derive some bounds on the Optimum Asymptotic Multiuser Efficiency (OAME) of randomly spread CDMA as extensions of the result by Tse and Verdú. To this end, random Gaussian and random binary

On Optimum Asymptotic Multiuser Efficiency of Randomly Spread CDMA

It is shown that the optimum detector in a Gaussian randomly spread CDMA system has a performance close to the single user system at high signal-to-noise ratio when K and N → ∞ and the loading factor, (K/N), is kept less than (log3 K/2).

A family of likelihood ascent search multiuser detectors: approaching optimum performance via random multicodes with linear complexity

  • Yi Sun
  • Computer Science
    IEEE Transactions on Communications
  • 2009
It is shown that the wide-sense sequential likelihood ascent search (WSLAS) detectors achieve unit AME with channel load < 1/2 - 1/(4 ln 2) bits/s/Hz and in simulations for random multicode equal-power systems, the WSLAS with a linear per-bit complexity approaches the GML BER in all SNR.

Tight Bounds on the Capacity of Binary Input Random CDMA Systems

An upper bound to the capacity of code-division multiple-access communication over a binary input additive white Gaussian noise channel is proved using random spreading and concentration of various relevant quantities is shown.

A Family of Likelihood Ascent Search Multiuser Detectors: Approach to Single-User Performance via Quasi-Large Random Sequence CDMA

  • Yi Sun
  • Computer Science
  • 2007
It is obtained that the WSLAS detector with a linear per-bit complexity achieves unit AME in the LRS-CDMA with a channel load < ½ − 1/(4ln2) bits/s/Hz.

A statistical-mechanics approach to large-system analysis of CDMA multiuser detectors

The performance of uncoded, fully synchronous, randomly spread code-division multiple-access (CDMA) multiuser detectors with additive white Gaussian noise (AWGN) channel, under perfect power control, and in the large-system limit is evaluated.

Approach to Optimum Performance in Random Spreading CDMA by Linear-Complex LAS Detectors

  • Yi Sun
  • Mathematics
    2007 41st Annual Conference on Information Sciences and Systems
  • 2007
A BER upper bound is applied to analyze the performance of local maximum likelihood (LML) detectors in large random spreading CDMA (LRS-CDMA) channels where user number A' and spreading gain N tend to infinity and KIN keeps a constant.

Iterative multiuser joint decoding: optimal power allocation and low-complexity implementation

This work optimize the received user signal-to-noise ratio (SNR) distribution in order to maximize the system spectral efficiency for given user channel codes, channel load, and target user bit-error rate.

Large-System Analysis of Static Multiuser Detection with an Unknown Number of Users

  • A. T. CampoE. Biglieri
  • Computer Science, Physics
    2007 2nd IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing
  • 2007
A study of large multiple-access communication systems in which multiuser detection is performed without knowledge of the number of interferers and the replica method is used as a key technique to compute the free-energy function and the macroscopic parameters that determine the multiusers efficiency and the bit error probability in the large system limit.



Spectral Efficiency of CDMA with Random Spreading

The CDMA channel with randomly and independently chosen spreading sequences accurately models the situation where pseudonoise sequences span many symbol periods. Furthermore, its analysis provides a

Optimum Multiuser Asymptotic Efficiency

  • S. Verdú
  • Computer Science
    IEEE Trans. Commun.
  • 1986
It is shown that the optimum multiuser efficiency of asynchronous systems is nonzero with probability 1, and therefore the optimum demodulator does not become multiple-access limited in contrast to the single-user receiver.

Capacity of CDMA fading channels

  • S. ShamaiS. Verdú
  • Computer Science
    1999 Information Theory and Networking Workshop (Cat. No.99EX371)
  • 1999
The key aspects of the fading multi-access model considered in this paper are: synchronous users with common processing gain N; random spreading sequences known at the receiver; slow independent

Effective bandwidth and effective interference for linear multiuser receivers in asynchronous channels

  • KiranDavid Tse
  • Computer Science
    1998 Information Theory Workshop (Cat. No.98EX131)
  • 1998
The analysis shows that in a system with large processing gain and random spreading sequences, there is no loss of performance due to asynchronicity in both the decorrelator and the MMSE receivers.

On the average near-far resistance for MMSE detection of direct sequence CDMA signals with random spreading

Tight upper and lower bounds on the expected near-far resistance of the MMSE detector are obtained, averaged over signature sequences and delays, as a function of the processing gain and the number of users.

Effective interference and effective bandwidth of linear multiuser receivers in asynchronous CDMA systems

It is shown that while the effective bandwidth of the decorrelator and the MMSE receiver is higher in an asynchronous system than that in a synchronous system, it progressively decreases with the increase in the length of the observation window and is asymptotic to that of the synchronous systems.

Output MAI distributions of linear MMSE multiuser receivers in DS-CDMA systems

The Gaussianity justifies the use of single-user Gaussian codes for CDMA systems with linear MMSE receivers, and implies that from the viewpoints of detection and channel capacity, signal-to-interference ratio (SIR) is the key parameter that governs the performance of the MMSE receiver in a CDMA system.

Capacity and mutual information of wideband multipath fading channels

The capacity and mutual information of a broadband fading channel consisting of a finite number of time-varying paths is investigated and it is shown that if white-like signals are used instead (as is common in spread-spectrum systems), the mutual information is inversely proportional to the number of resolvable paths L/spl tilde/ with energy spread out.

Optimal sequences, power control and capacity of synchronous CDMA systems with linear multiuser receivers

The capacity of networks with multiuser receivers together with efficient usage of the resources, is analyzed in the uplink scenario of a single cell synchronous code division multiple access (CDMA)

Optimal sequences, power control, and user capacity of synchronous CDMA systems with linear MMSE multiuser receivers

It turns out that with this optimal allocation of signature sequences and powers, the linear MMSE receiver is just the corresponding matched filter for each user, and the effect of transmit power constraints on the user capacity is characterized.