According to the technical research and outfield experiment in TD-LTE commercial network, downlink coordination between cells based on coordinated multiple points(Co MP) technique is presented in this paper. Without changing the deployment of existing base stations and transmission equipments, it can improve the throughput of the users at the cell boundary, enhance the quality of experience and improve the competitiveness of TD-LTE industry.

The uplink coordination in LTE system is mainly based on soft combining, and is suitable for cells connected with ideal transport condition, but it is difficult to deploy. According to the principle of multi-cell joint detection in TD-SCDMA system,the technique of cloud interference rejection combining ( Cloud IRC) is proposed,and it can be used between cells without ideal transport condition. According to test in commercial LTE network,the throughput of cell-edge users can be improved by 89. 9% on average with the technique of soft combining,and 29. 3% with the technique of Cloud IRC. With both of them,the quality of experience is improved in the whole network.

This paper considers the channel estimation in the long term evolution(LTE) downlink system.We introduce the linear minimum mean squared error(LMMSE) estimation algorithm which is used in frequency domain and time domain.Following this,we propose some methods like mismatched model or sliding window.The proposed method reduces the complexity of LMMSE algorithm in avoiding the complicated calculation in channel correlation matrix and a large number of data to be saved.At last,we use added pilot,pre-subframe and post-subframe data to improve the estimation performance.Simulation results show that the proposed methods can significantly improve the system performance in low complexity.

A sequential antenna selection algorithm for dual-stream transmission in TD-HSPA + (time division-high speed uplink packet access plus) 8-antenna downlinks is proposed. Firstly, according to the system model, the individual SNR (signal to noise ratio) formula of dual-stream after eigen-beamforming is derived. Based on the derived formula, five kinds of antenna selection criteria are designed, and a sequential selection algorithm instead of a greedy method is introduced to select antennas with less complexity. Simulation results show that the performance of maximizing the second largest eigenvalue of equivalent channel correlation matrix is optimal among the five selection criteria. In contrast to the greedy selection algorithm, selecting antennas in sequential way only causes 0.1 dB performance degradation while in latter case the computation burden is only one fourth of that in the former one.

In 3GPP long term evolution(LTE) physical layer downlink,the hybrid automatic request(HARQ) based on the transmission block(TB) is utilized in order to obtain better data throughputs in various test cases for the mobile terminals.Since the different code blocks(CB) in one TB are turbo coded independently,the decoding status for individual CBs always vary considerably in the receiving process of TB.The receiver can set the decoding status for each CB according to the cyclic redundancy check.Due to the capacity limit of the uplink channel,the receiver can only feedback one bit for each TB and the all data in the TB will be retransmitted even though there is only one CB decoding failure.By the linear coding of the data in different TBs,the network coding technology can improve the data throughput efficiently.According to the characteristics of the LTE downlink transmissions,we propose a joint HARQ of multiple processes based on network coding.In the proposed HARQ schemes,the retransmissions of the multiple processes are scheduled jointly by an added feedback bits to indicate network coding process,after each TB has been transmitted once.The flowcharts for the proposed HARQ are given,where the transmitting and receiving process both can work efficiently according to the added feedback bit for network coding indication.In the comparison of the throughput simulations,the new HARQ scheme based on network coding can achieve obvious performance gain over the LTE-HARQ schemes,while the only one feedback bit is added for the transmissions of multiple processes.

Load control is an important component of wireless resource management (RRM). It detect system load in period and provide a suitable solution to make sure that system load below threshold. Load control algorithms can be devised from a multi-cell perspective. This allows the reduction of the load in a given reference cell. In particular, this can be beneficial when service distribution is not homogeneous in the scenario. The paper present an algorithm that forbidden the transmission of users in neighbour cells to reduce the intercell interference in reference cell and thus reduce the load in reference. We can draw the conclusion from the result of simulation that the algorithm perform well.

This paper studies the uplink load control strategies of TD-SCDMA system combined with the characteristics and standards of trunking service. Through the simulation, we propose an appropriate uplink load control strategy for TD-SCDMA trunking system, which is based on existing protocol standards. The congestion detection is at base station, while the congestion solution is at RNC. Through a period of measuring, evaluate the load status of every base station. Drop calls of users with bad QoS in overloaded base station, so as to improve the overall performance of the system.

Broadcast transmission is used in the downlink for TD-SCDMA trunking systems in the same frequency and same time slot, so the MAI of multi-cell is very serious. In this paper, we discuss the classical joint detection algorithms used for interference suppression. Considering the characteristics of trunking system, we can consider multi-cell model as macro-diversity model, when users of target group are distributed in different cells. We simulate under three different channel models (described in section 2), and it is shown that joint detection and macro-diversity can significantly improve system performance. The impairing effect of error propagation on macro-diversity depends on the distribution of the target group.

TD-SCDMA truncking system is a developing direction in digital truncking system. Based on TD-SCDMA trunking system, a movable boundary dynamic channel allocation (MB DCA) scheme is proposed. The characteristic of the algorithm is that the data service can borrow the voice channel for data transmission when the voice channel is idle and the data register queue is not empty. When a new voice call comes in, data service is blocked and voice service re-occupies the channel. The simulation results show that the channel utilization have an effectively improvement.

Coordinated multi-point transmission/reception (CoMP), in which base stations cooperation during the downlink, has been considered as a attractive way of achieving higher performance and mitigating interference, especially for terminals at cell edges. In this paper, distributed precoding for multicell-MISO downlink CoMP is considered. Most previous work in the area is on the assumption that base stations have knowledge of both data symbols and full channel state information (CSI), which leads to heavy exchange of channel state information and signal information over backhaul links . In this paper, several distributed precoding strategies (Distributed MRT, distributed ZF, distributed LVSINR and DVSINR) for multicell-MISO downlink CoMP are analyzed, which supposes that each base station only has local CSI and the precoders can be devised at each BS in a distributed manner, and Monte Carlo simulations demonstrate the performance of such strategies.

Broadcast transmission is used in the downlink of TD SCDMA trunking systems with the same frequency and same time slot macro-diversity model, and base stations transmit the same signal simultaneously. Signal that target user receives from neighbor cells is useful instead of interference, which can strengthen the useful signal and lower the interference. Motivated by this fact, we discuss three types of receivers in this paper. They are matched-filter receiver, receiver with method 1 (with perfect channel estimation), receiver with method 2 (linear combination). Moreover, the system performance of the above receivers in three typical scenarios is simulated and analyzed.

Block diagonalization (BD) is a classical and practical interference cancelation precoding algorithm in MU-MIMO system. But once BD is used, the user number can be supported simultaneously by the base station is limited by the ratio of the numbers of transmit and receive antennas. In this paper, some existed lower complexity user selected schemes are discussed. These schemes are all based on capacity as the performance measure. However, there is an inherent drawback in these algorithms. Since the BS always selected the same users based on capacity or the correlation of the users in each time slot, it may not guarantee the quality-of-service of a single user. In order to ensure fairness in some systems, we improve the existed algorithms and propose the round-robin user selection algorithms.

In this paper, we discuss the bit-interleaved coded modulation (BICM) for the half-duplex decode-and-forward (DF) relay network based on the protograph LDPC codes. The half- duplex relay BICM design problem can be transformed into a problem of rate-compatible BICM design, where the different segments of modulated symbols experience different SNRs. To optimize the BICM based on the rate-compatible protograph structure, we use the protograph extrinsic information transfer (EXIT) to evaluate the thresholds of different mapping patterns between the variable nodes in protographs and the modulated bits. With this tool, we search the efficient mapping pattern of BICM for the half-duplex DF network. Our work can achieve significant gains over the existing work.

A type of synchronous prime-hop codes is presented for hybrid direct sequence/frequency hopping optical code division multiple access (DS/FH-OCDMA) system. And a novel scheme for DS/FH-OCDMA system with array waveguide gratings based encoder/decoder is designed. Further, a detailed performance analysis of the system is given. The results reveal that the scheme is easy to plan, and has large number of simultaneous user and low bit error rate.