Robert Soni

Interference management for 4G cellular standards [WIMAX/LTE UPDATE]

4G cellular standards are targeting aggressive spectrum reuse (frequency reuse 1) to achieve high system capacity and simplify radio network planning. The increase in system capacity comes at the expense of SINR degradation due to increased intercell interference, which severely impacts cell-edge user capacity and overall system throughput. Advanced interference management schemes are critical for achieving the required cell edge spectral efficiency targets and to provide ubiquity of user experience throughout the network. In this article we compare interference management solutions across the two main 4G standards: IEEE 802.16m (WiMAX) and 3GPP-LTE. Specifically, we address radio resource management schemes for interference mitigation, which include power control and adaptive fractional frequency reuse. Additional topics, such as interference management for multitier cellular deployments, heterogeneous architectures, and smart antenna schemes will be addressed in follow-up papers.

Design of Rate-Compatible Irregular LDPC Codes Based on Edge Growth and Parity Splitting

This paper considers the design of rate-compatible low-density parity-check (LDPC) codes with optimized degree distributions for their corresponding rates. The proposed design technique is based on extension, where a high-rate base code, or daughter code, is progressively extended to lower and lower rates such that each extension code is compatible with the previously obtained codes. Specifically, two well-known parity matrix construction methodologies, edge growth and parity splitting, are adapted to yield a flexible framework for constructing rate- compatible parity check matrices with a uniform performance characteristic. The design examples provided are based on extrinsic information transfer (EXIT) chart optimizations and demonstrate good performance up to rates as low as 1/5.

Video telephony over downlink LTE systems with/without QoS provisioning

More and more video application are being carried on wireless systems with the development of the smart phones. However, the performance of these applications is lack of study, especially for the most advanced LTE networks. In this paper, we investigate the performance of the video telephony over the LTE downlink systems with and without QoS provisioning. The simulation results using two classical algorithms: proportional fair scheduler (PF) and proportional fair scheduler with minimum/maximum rate constraints (PFMR) are presented. Both pure video telephony traffic scenario and two-service scenario of mixed video with full buffer traffics are considered in this paper. The simulation results show that the video capacity is mainly limited by the delay of the video users and the video capacity is increased using PFMR compared with PF, which shows the benefit of providing QoS provisioning. The paper also shows the delay and throughput is highly related to the geometry of the users. The worse the users geometry is, the user experiences the longer delay and achieves the smaller throughput.

Self-organizing interference management for LTE

In orthogonal frequency division multiple access (OFDMA) systems such as Long Term Evolution (LTE), it is extremely important to reduce interference between neighboring cells, especially for cell edge users, since the only interference in LTE is inter-cell interference due to the orthogonality of the sub-carriers used in the transmissions. This paper describes a few self-organizing and self-optimizing techniques to manage and reduce this inter-cell interference. These self-optimizing network (SON)-based techniques are inter-cell interference coordination (ICIC) and uplink (UL) interference over thermal (IoT) control. Simulation results are presented showing the improvements that can be obtained with the use of such techniques in interference limited operating scenarios.

Transmit Diversity With More Than Two Antennas

Recently, a new form of transmit diversity has been developed and included for cdma2000, the third generation successor for IS-95 code division multiple access (CDMA) systems. This transmit diversity scheme was developed by Bell Laboratories and uses Space-Time coding techniques. This paper presents performance results of this new transmit diversity method, termed space-time spreading, and investigates ”open-loop” improvements to the scheme which use more than two antennas. Additionally, we investigate the performance improvements possible with closed loop techniques.