Information Capacity of the Space Division Multiple Access Mobile Communication System

An expression for the Shannon capacity lower bound of the space division multiple access (SDMA) mobile communication channel with interference is shown. The bound is tightly approaching the Shannon capacity of the orthogonal SDMA system over Gaussian channel with no interference. The information capacity of the SDMA system with adaptive MMSE receivers is presented as well. The SDMA system with MMSE receivers achieves at least 50% of the orthogonal SDMA system capacity for the input signal to noise ratio of practical interest in cellular mobile communications (10-30 dB)

CMA-based Code Acquisition Scheme for DS-CDMA Systems

In direct-sequence code-division multiple access, a code synchronization must take place before the multiuser detector. As the initial synchronization stage, code acquisition scheme is used to estimate the relative timing phase for the desired transmission within one chip interval. In this paper, a blind code acquisition scheme using adaptive linear filtering based on a linearly constrained constant modulus algorithm (CMA) is proposed. The uncertainty of a desired user's delay is initially discretized and translated into a number of hypotheses. The lock convergence property of CMA is exploited, where the filter at the steady state can lock onto the desired user while nulling all other interfering users (i.e., a decorrelator). For each delay hypothesis, the filter is initialized as the corresponding shifted spreading sequence of the desired user. It is shown that lock convergence always occurs for the correct hypothesis, while all incorrect hypotheses will be hovered around some saddle regions, given sufficiently small step sizes. Then, the correct hypothesis is the one which has the converged filter to yield the maximum lock onto the desired user, or a maximum output energy

Ultra-wideband cognitive interrogator network: Adaptive illumination with active sensors for target localisation

The authors explore the potential application of cognitive interrogator network (COIN) in remote monitoring of mobile subjects in domestic environments, where the ultra-wideband radio frequency identification (UWB-RFID) technique is considered for accurate target localisation. The authors first present the COIN architecture in which the central base station (BS) continuously and intelligently customises the illumination modes of the distributed interrogators in response to the system's changing knowledge of the channel condition and subject movement. Subsequently, the analytical results of the locating probability and time-of-arrival (TOA) estimation uncertainty for a large-scale COIN with randomly distributed active sensors are derived based upon the implemented cognitive intelligence. As an important component to facilitate the adaptive illumination of the environment, the sequential-hypothesis-testing framework is proposed to estimate the tag antenna orientation. Finally, numerical examples are used to demonstrate the key effects of the proposed cognitive schemes on the system performance

The performance of turbo codes for wireless communication systems

Turbo codes play an important role in making communications systems more efficient and reliable. This paper provides a description of two turbo codes algorithms. Soft-output Viterbi algorithm and logarithmic-maximum a posteriori turbo decoding algorithms are the two candidates for decoding turbo codes. Soft-input soft-output (SISO) turbo decoder based on soft-output Viterbi algorithm (SOVA) and the logarithmic versions of the MAP algorithm, namely, Log-MAP decoding algorithm. The bit error rate (BER) performances of these algorithms are compared. Simulation results are provided for bit error rate performance using constraint lengths of K=3, over AWGN channel, show improvements of 0.4 dB for log-MAP over SOVA at BER 10-

Novel channel description method for decentralized wireless relay networks

We present a novel channel model for a two-hop decentralized wireless relay network (DWRN), where the relays operate in a completely distributive fashion. The model is based on an analogous approach to the conventional description methods for wideband directional multipath channels. Specifically, the notion of information azimuth-delay spectrum (IADS) is devised. This definition, parallel to the widely-used power azimuth-delay spectrum (PADS) for physical multipath channels, represents a compact description of virtual DWRN channels. The proposed approach is also applied to a circular random network (CRN) with uniformly-distributed relay nodes. Finally, numerical examples are used to demonstrate the usefulness of the suggested channel description method

Ultra-wideband cognitive interrogator network for indoor location tracking - part 1: system architecture and network performance analysis

We explore the potential application of cognitive interrogator network (CIN) in remote monitoring of mobile subjects in domestic environments, where the ultra-wideband radio frequency identification (UWB-RFID) technique is considered for accurate source localization. We first present the CIN architecture in which the central base station (BS) continuously and intelligently customizes the illumination modes of the distributed transceivers in response to the systempsilas changing knowledge of the channel conditions and subject movements. Subsequently, the analytical results of the locating probability and time-of-arrival (TOA) estimation uncertainty for a large-scale CIN with randomly distributed interrogators are derived based upon the implemented cognitive intelligences. Finally, numerical examples are used to demonstrate the key effects of the proposed cognitions on the system performanc

Adaptive MMSE multiuser receivers in MIMO OFDM wireless communication

This paper presents a novel adaptive multiuser detection scheme for MIMO OFDM, which we refer to as AMUD MIMO OFDM. It combines the adaptive minimum mean square error multiuser detection scheme with prior information of the channel and interference cancelation in the spatial domain. Simulation results show that joint channel parameters estimation has good performance compared to individual parameter estimation. The developed algorithm sum rate capacity is close to MIMO theoretical upper bound (21.5 bits/s/Hz at an SNR of 20dB) which indicates its applicability to the uplink channel, where power ransmission at the mobile station is a constraint. The BER performance shows that an 8 x 8 AMUD MIMO OFDM provides a 2dB SNR gain as compared to non adaptive MIMO OFDM