Connectivity is the backbone of the networked intelligence stack. In particular, wireless connectivity using licensed spectrum is critical for network intelligence applications requiring mobility and service quality. The latest cellular technology, i.e., the 5G network, provides a flexible, scalable, agile, and programmable platform to manage various applications with diverse requirements within the same network. However, since the 5G network is built on cellular architecture, the user’s performance at the cell-edge is limited. The cell-edge user in traditional cellular network experiences degraded quality of service compared to cell-center user due to path loss and interference from neighboring base stations. Cell-free is a promising technology that can improve the cell-edge performance as it offers macro-diversity and consequently improved coverage and throughput. Moreover, the network capacity in a cellular network is often underutilized due to a static TDD configuration coupled with asymmetric traffic demands in neighboring cells. To handle heterogeneous traffic demands, dynamic TDD is considered to be a beneficial technology, wherein different cells can independently schedule slots in the uplink/downlink directions depending on their local traffic demands. However, dynamic TDD brings new challenges because of the introduction of new cross-link interferences (CLI) between users and between base stations. Combining cell-free MIMO with dynamic TDD can effectively overcome the CLI, as there exists inbuilt co-operation between the access points in the cell-free MIMO architecture. Cell-free with dynamic TDD provides high spectral and energy efficiency, greater reliability, increased coverage probability, macro-diversity gain, interference suppression, and simple signal processing. This makes it suitable for next-generation indoor and hot-spot coverage scenarios, such as a smart factory, train/metro stations, small villages, shopping complexes, stadiums, hospitals, college campuses, etc. and critical outdoor coverage scenarios, such as a connected and autonomous vehicles, etc. This research work presents the hardware implementation of cell-free and dynamic TDD using the OpenAirInterface 5G new radio software stack, with the aim to experimentally understand the role of cell-free and dynamic TDD in providing better connectivity at the celledge and improving network throughput. It was a joint project with Sanjhi Gupta. My role in the project was to implement cell-free architecture with distributed processing, configuration of dynamic TDD and integration of cell-free and dynamic TDD system. The prototype of cell-free with dynamic TDD on 5G Testbed was successfully established and the measurements of individual setups for cell-free and dynamic TDD shows improvement over cellular network
We have submitted the extended abstract at WSA 2021 conference. Title: Hardware Implementation and Evaluation of Cell-Free MIMO and Dynamic TDD using the OAI Codebase.
Himani Kamboj, Bhawesh Anand, Sanjhi Gupta, Ashish Meshram, Sudhakar Balijepalli, and Chandra R. Murthy
Our project has been shortlisted in the top 100 entries in DoT’s 5G Hackathon. We have submitted the final prototype and are waiting for the next phase result