Radio Interface Evolution Towards 5G and Enhanced Local Area Communications

Abstract

The exponential growth of mobile data in macronetworks has driven the evolution of communications systems toward spectrally efficient, energy efficient, and fast local area communications. It is a well-known fact that the best way to increase capacity in a unit area is to introduce smaller cells. Local area communications are currently mainly driven by the IEEE 802.11 WLAN family being cheap and energy efficient with a low number of users per access point. For the future high user density scenarios, following the 802.11 HEW study group, the 802.11ax project has been initiated to improve the WLAN system performance. The 3GPP LTE-advanced (LTE-A) also includes new methods for pico and femto cell's interference management functionalities for small cell communications. The main problem with LTE-A is, however, that the physical layer numerology is still optimized for macrocells and not for local area communications. Furthermore, the overall complexity and the overheads of the control plane and reference symbols are too large for spectrally and energy efficient local area communications. In this paper, we provide first an overview of WLAN 802.11ac and LTE/LTE-A, discuss the pros and cons of both technology areas, and then derive a new flexible TDD-based radio interface parametrization for 5G local area communications combining the best practices of both WiFi and LTE-A technologies. We justify the system design based on local area propagation characteristics and expected traffic distributions and derive targets for future local area concepts. We concentrate on initial physical layer design and discuss how it maps to higher layer improvements. This paper shows that the new design can significantly reduce the latency of the system, and offer increased sleeping opportunities on both base station and user equipment sides leading to enhanced power savings. In addition, through careful design of the control overhead, we are able to improve the channel utilization when compared with LTE-A.

Distributed CSI Acquisition and Coordinated Precoding for TDD Multicell MIMO Systems

“…Data transmission thus takes place between the filter updates of the algorithm. The ratio between uplink and downlink data transmission lengths could be flexibly allocated [32]. Before the iterative algorithm has converged, the data rates that are achievable in the downlink data transmission phase may be low, but not negligible, as shown by the numerical results in Sec.…”

“…As a brief example, under a block fading channel with carrier frequency f c = 2 GHz and UE speed v = 3 km/h, the coherence time can be modeled as T c = 1 2fc c v = 90 ms [33]. For future 5G systems, the TDD switching periodicity is planned to be 1 ms or less [32], [34], leading to at least 5 We remind the reader that our notion of 'CSI' encompasses knowledge of the effective channels and the covariance matrices; see Tables I and II. 90 uplink-downlink iterations in one coherence interval when the UEs are slowly moving. In continuous fading channels, the proposed algorithm would possibly instead be able to track the channel variations, assuming that they are slow enough.…”

Evaluation of SPMA and higher order sectorization for homogeneous SIR through macro sites

“…In order to achieve these objectives, different solutions are proposed in the literature [14][15][16][17][18]. One solution is the densification of sites, and concentrates on improving the small scale communications.…”

Development of Wireless Access and Flexible Networking Technologies for 5G Cellular Systems

“…Since around 2010, the 5G system development was started, and its common understanding is that 5G should be sharply evolved from 4G; i.e., 1) its service is expanded from information transfer services to "connected" services [1]- [3] that connect vertical sectors [4] which are not connected to cellular systems yet, 2) more number of services, especially related to low latency-required services should be supported based on end-to-end quality of services (QoS) guaranteed services [5], and 3) dynamic control functionality is expanded to network in addition to the wireless access to cope with flexible end-to-end QoS support [5]. The first item means, 5G will actively introduce connection services for internet of things (IoT) in addition to the enhanced mobile broadband (eMBB) services [6].…”