This paper evaluates the throughput of a distributed antenna network (DAN) with multiple mobile terminal scheduling and the usage of joint maximum-likelihood detection (MLD). Mobile terminals are closer to the desired antennas in the DAN which leads to higher throughput and better frequency utilization efficiency. However, when multiple mobile terminal scheduling is applied to the DAN, interference can occur between transmitted signals from antennas. Therefore, in this research, mobile terminal scheduling along with joint MLD is applied to reduce the effects of interference. A system level simulation shows that the usage of joint MLD in a densely packed DAN provides better system throughput regardless of the numbers of mobile terminals and fading channels.

Non-orthogonal multiple access (NOMA) makes multiple mobile users share the same frequency band. In a conventional NOMA scheme, a user pair that can be assigned to the same frequency resource is limited, which reduces the amount of capacity improvement possible. This is because a far user demodulates a signal without canceling an underlaid signal for a near user. In addition, semi-orthogonal multiple access (SOMA) modulation has been proposed. This modulation scheme helps to reduce scheduling complexity and demodulation complexity. In this paper, a joint detection scheme is applied to a far user as well as a near user in a NOMA downlink. The joint detection in the far user leads to a more number of user pairs that can be assigned to the same frequency resource through proportional fair scheduling. The total system throughput performance with the joint detection is evaluated with multi-cell system level simulation. Numerical results show that the joint detection in the original NOMA system increases the system throughput more effectively than that with SOMA modulation.

In this paper, a multi-cell joint channel estimation (JCE) method is proposed for the TD-SCDMA downlink. In the proposed multi-cell JCE approach, the received midambles from adjacent cells are jointly processed, rather than being treated as interference as in single cell channel estimation. By jointly processing all the received midambles, the user can simultaneously estimate the channel impulse responses (CIRs) for both its home cell and adjacent cells. If the received signal from adjacent cells has a delay, multi-cell JCE is still operable with slight adjustment in the midamble matrix, and the performance loss is also minor. The performance of multi-cell JCE is analyzed and evaluated by simulations. The results demonstrate that the proposed multi-cell JCE method can significantly improve the channel estimation accuracy. When the signal from each cell has similar power level, the mean square error (MSE) of the estimated CIRs for all cells is lower than 0.01. With more accurate CIRs from multi-cell JCE, multi-cell JD also yields better performance compared with the single cell channel estimation methods.

This paper focuses on the investigation of RoF link noise influence in an ubiquitous antenna system, which is composed of multiple radio base stations (RBSs) deployed over the service area, central control station (CCS) and radio-on-fiber (RoF) link that connects RBSs to the CCS. The ubiquitous antenna system is capable of receiving multiple mobile terminals simultaneously operating at the same frequency channel by making effective use of joint detection. However, in the ubiquitous antenna system, since signals are transmitted from RBSs to CCS via the RoF link, the noise generated at the RoF link, such as relative intensity noise, inter modulation distortion, optical shot noise and thermal noise, may become dominant factors degrading the performance. The performance evaluations considering optical link noise is given by computer simulations. Computer simulation results show that more than 19 dB of RoF link Eb/N0 is required for achieving sufficient performance.

In this letter, we study the performance of the iterative receiver as applied to the space division multiplexing/orthogonal frequency division multiplexing (SDM/OFDM) systems. The iterative receiver under consideration employs the soft in/soft out (SISO) decoding process, which operates iteratively in conjunction with channel estimation for performing data detection and channel estimation at the same time. As opposed to the previous studies in which the perfect channel state information is assumed, the effects of channel estimation are taken into account for evaluating the performance of the iterative receiver and it is shown that the channel estimation applied in every iteration step of the iterative receiver plays a crucial role to warrant the performance, especially at a low signal-to-noise power ratio (SNR).

In this paper, we propose a new coded orthogonal frequency division multiplex (COFDM)-based ubiquitous antenna system, which is composed of multiple radio base stations (RBSs) deployed over the service area and Radio-on-Fiber (RoF) link that connects RBSs to the central control station (CCS). The proposed system is capable of receiving multiple mobile terminals simultaneously operating at the same frequency by making effective use of joint detection. However, the propagation delay due to the RoF link could be a major problem for realizing the ubiquitous antenna system. In order to overcome this delay problem, we assume that the guard interval of COFDM is longer than the delay difference. Furthermore, in order to improve BER performance in a multipath Rayleigh fading channel, we also propose the MSE normalization scheme followed by the use of an MMSE-based joint detector. Computer simulation results show that the proposed system can improve the frequency utilization efficiency of the broadband wireless access system.

In this contribution an algorithm for joint detection in fast frequency hopping/multiple frequency shift keying (FFH/MFSK) multiple access (MA) systems is presented. The new algorithm - referred to as REC algorithm - evaluates ambiguities which occur during the decision process and iteratively reduces the number of candidate symbols. The REC algorithm is of low complexity, suitable for every addressing scheme, and effective for both an interference-only channel and a fading channel. For the interference-only channel the REC algorithm enables maximum likelihood (ML) joint detection with low computational effort.