Low latency relaying schemes for next-generation cellular networks

Abstract

Abstract-The reduction in both user and control plane latency is a major goal for next generation (4G) cellular networks, specifically the Long Term Evolution-Advanced (LTE-A) standard. At the same time, relay stations, which introduce additional latency into transmissions, are seen as a potential means to improve cell spectral efficiency and coverage. This paper extends a number of existing relaying schemes to the case where a stricter latency constraint is applied. These low latency schemes are first evaluated for convolutional codes, for which they quickly approach the performance of full decoding at the relay with little additional latency over memoryless relaying. The schemes are then adapted for the turbo code in the LTE standard and shown to be preferable to full decoding and memoryless relaying for certain LTE-A relay types.

Novel noncoherent detection for multi‐hop amplify‐and‐forward relaying systems

“…approximated to 1 lR and 0 lR (using 1 l and 0 l to represent), respectively. Substitute (7) into (18), one has the following: 1 symbols are used in the simulation. To evaluate the effect of the number of hops, N is set to 2, 4, or 6.…”

“…If coherent detection is used, this non-Gaussian sample is not a problem, as the sample conditioned on the fading gains is still Gaussian and the fading gains are known in coherent detection such that the optimal coherent detector based on the Gaussian assumption is still applicable [7][8][9][10]. However, coherent detection requires knowledge of fading gains, which has to be obtained via channel estimation.…”

On Optimal Latency of Communications

“…Over long distance ranges, wireless relaying schemes could be an efficient solution for low-latency communication. Several works has been dedicated to this purpose [1]- [4]. To our knowledge, these research works might not be optimal for lowlatency communication.…”

“…Ideally, when the messages are long, one can reduce latency by using decode-and-forward (DF) schemes by dividing the message into smaller parts. However, the receiver must wait an entire codeword before determining any of the input symbols which yields greater computational complexity and latency [1]. On the other hand, if one does not have a receive power or error probability issue, an amplify-and-forward (AF) scheme has relatively low complexity and minimal latency [1].…”

A Novel Machine-to-Machine Traffic Multiplexing in LTE-A System Using Wireless In-Band Relaying

“…Out-band relaying operations performance optimization is investigated in [18]. In [19], the reduction in relaying latency is discussed by extending the available relaying schemes. The issue of QoS-aware scheduling for relays with in-band operations is discussed in [20].…”