A PHY-layer framework of multirate transmission for ultra-dense networks in 5G

Future wireless communication systems beyond 2020 will demand diverse requirements on system design that supports a wide range of data rates in overcrowded networks. This paper presents a physical (PHY)-layer system design for ultra-dense network (UDN) with multirate transmission. This proposed scheme transmits user data over highly fragmented spectrum which implies efficient spectrum utilization. This approach may be considered as a potential PHY-layer design for 5-th generation (5G) networks, as it supports both integer and fractional multiple of basic data rates which yield diverse quality-of-service (QoS) requirement with non-contiguous spectrum allocation for future wireless applications and services. Simulation results show the improved bit-error-rate (BER) performance for higher data rate users in the proposed system design. However lower data rate users suffers from high level of interference due to the low spreading gain diversity. Further to improve the performance of high and low data rate users, we use forward error correcting codes like low-density parity-check (LDPC) codes at the cost of throughput. It is observed that the performance improvement due to error correcting codes is more in lower data rate users due to less data used in LDPC encoder compared to higher data rate users. Thus, we can ascertain reasonable BER performance for both low and high data rate users even in overloaded scenario. This paper suggests a novel approach towards the development of a new PHY-layer design for 5G.