Project Objectives:

The project aims at developing a channel coding solution suitable for millimeter wave (mm-wave) communications for 5G wireless systems. This work comprises of studying the channel model being standardized for 5G wireless, explore the feasibility of several channel coding schemes from their theoretical performance to hardware implementation for such a model and designing a scheme that satisfies the requirements of certain subsets of the 5G umbrella of requirements.

Technology Rationale:

5G wireless is expected to provide data rates of up to ten gigabits per second with an overall latency of less than 1ms for the next generation of wireless technology. Although the migration to mm-wave bands offers a huge increase in the available bandwidth relative to the currently deployed cellular networks, it comes with propagation challenges such as, heavy reliance on directional communication, short range of communication, increased shadowing and rapid fading in time. In spite of these challenges, mm-wave communication has been successfully employed for short range indoor environments such as those seen in the IEEE 802.11ad and the IEEE 802.15.3c systems. However, the relatively long-range outdoor communication environment presents further difficulties. In addition to the frequency dependent free-space path loss, penetration losses due to commonly used building materials such as concrete and bricks can be upwards of 150 dB. In addition, human blockage can result in up to 25-30dB loss. While several types of channel codes (for e.g. convolutional, Turbo and LDPC) are already being used in contemporary systems such as the IEEE 802.11 and the 3GPP LTE, there is still a need to have code structures that perform at a very high throughputs and low latencies while operating near capacity; and are suitable for an outdoor environment where directional link blockages are possible.

Technology Approach:

The challenges above mean that, relative to contemporary systems, the processing complexity of the system (especially the already time and space constrained mobile terminal) will only increase. We aim at designing codes for the mm-wave channel that provide a wide range of rates and lengths while having a good performance. While satisfying the code rate and length requirement, it is crucial to design codes that are amenable to encoder-decoder implementations that operate at several Gb/s with low-latency. To achieve this, we analyze and study the encoding and decoding algorithms and optimize them such that a high-throughput, low-latency implementation can be developed using them. Below figure summarizes our underlying research methodology.

Project Status:

We have proposed various techniques to achieve a high-throughput decoder architecture for the Min-Sum Approximation (MSA) algorithm for Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes. To validate the architecture, an IEEE 802.11n (2012) decoder is implemented which attains a throughput of 608Mb/s (at 260MHz) and a latency of 5.7 microseconds on the Xilinx Kintex-7 FPGA. An application of the above mentioned architecture is a standalone IEEE 802.11n (2012) standard compliant decoder achieves an overall throughput of 2.48Gb/s at an operating frequency of 200MHz on the Xilinx Kintex-7 FPGA in the NI USRP-2953R. With little or no modification, this decoder can be applied to a large family of standard compliant QC-LDPC codes such as those specified in IEEE 802.16e and Digital Video Broadcast (DVB). Another application to demonstrate the flexibility of the architecture and the rapid-prototyping capability of the tools used is presented as a Hybrid-ARQ system using LDPC codes. To study the effect of environmental blockages after beamforming, we have proposed a hierarchical blockage model and presented the results associated with it. The simulation of the channel model being standardized by the 3GPP is underway along with the development of a suitable coding scheme for the same.