Abstract

The use of millimeter wave (mmWave) frequencies for communication will be one of the innovations of the next generation of cellular mobile networks (5G). It will provide unprecedented data rates, but is highly susceptible to rapid channel variations and suffers from severe isotropic pathloss. Highly directional antennas at the transmitter and the receiver will be used to compensate for these shortcomings and achieve sufficient link budget in wide area networks. However, directionality demands precise alignment of the transmitter and the receiver beams, an operation which has important implications for control plane procedures, such as initial access, and may increase the delay of the data transmission. This paper provides a comparison of measurement frameworks for initial access in mmWave cellular networks in terms of detection accuracy, reactiveness and overhead, using parameters recently standardized by the 3GPP and a channel model based on real-world measurements. We show that the best strategy depends on the specific environment in which the nodes are deployed, and provide guidelines to characterize the optimal choice as a function of the system parameters.

Highlights

  • The 5th generation (5G) of mobile cellular networks is currently being standardized by the 3GPP as NR [1], and is designed to enable a fully mobile and connected society, in order to address the tremendous growth in connectivity and density/volume of traffic that will be required in the near future [2]

  • The extreme propagation environment at mmWave frequencies requires the adoption of directional transmissions and beamforming techniques, which increase the achievable data rate and the latency and overhead required to perform Initial Access (IA)

  • In this paper we evaluated, with an extensive analysis and simulation campaign, the impact of several parameters on the performance of multiple IA schemes for NR networks operating at mmWaves

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Summary

INTRODUCTION

The mmWave spectrum – roughly comprised between 10 and 300 GHz – has been considered as an enabler of the 5G performance requirements in micro and picocellular networks [3] These frequencies offer much more bandwidth than current cellular systems, which are allocated in the congested bands below 6 GHz, and initial capacity estimates have suggested that mmWave networks offer orders of magnitude higher bit-rates than 4G systems [4]. Directional links, require fine alignment of the transmitter and the receiver beams, a procedure which might greatly increase the time it takes to access the network In this regard, defining efficient Initial Access (IA) procedures, which allow a mobile UE to establish a physical link connection with a gNB (a necessary step to access the network), is challenging at mmWave frequencies [7]. In the mmWave bands, it may be essential to exploit the antenna gains already during the IA phase, otherwise there would be a mismatch between the range at which a cell can be detected (control-plane range), and the much longer range at which a user could directionally send and receive data using beamforming (user-plane range)

Related Work
INITIAL ACCESS FRAMEWORKS
Performance Metrics
RESULTS AND DISCUSSION
Detection Accuracy Results
Reactiveness Results
Overhead Results
Final Considerations
CONCLUSIONS
Full Text
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