Abstract
Long-Term Evolution (LTE) and its improvement, Long-Term Evolution-Advanced (LTE-A), are attractive choices for Machine-to-Machine (M2M) communication due to their ubiquitous coverage and high bandwidth. However, the focus of LTE design was high performance connection-based communications between human-operated devices (also known as human-to-human, or H2H traffic), which was initially established over the Physical Random Access Channel (PRACH). On the other hand, M2M traffic is mostly based on contention-based transmission of short messages and does not need connection establishment. As a result, M2M traffic transmitted over LTE PRACH has to use the inefficient four-way handshake and compete for resources with H2H traffic. When a large number of M2M devices attempts to access the PRACH, an outage condition may occur; furthermore, traffic prioritization is regulated only through age-based power ramping, which drives the network even faster towards the outage condition. In this article, we describe an overlay network that allows a massive number of M2M devices to coexist with H2H traffic and access the network without going through the full LTE handshake. The overlay network is patterned after IEEE 802.15.6 to support multiple priority classes of M2M traffic. We analyse the performance of the joint M2M and H2H system and investigate the trade-offs needed to keep satisfactory performance and reliability for M2M traffic in the presence of H2H traffic of known intensity. Our results confirm the validity of this approach for applications in crowd sensing, monitoring and others utilized in smart city development.
Highlights
In many smart city application scenarios—from building monitoring and healthcare monitoring, through smart parking and smart city lighting, to crowd sensing and vehicular safety applications—a large number of smart devices send their messages to appropriate servers for further analysis and actions, as Figure 1 schematically shows
M2M messages can be transmitted using Long-Term Evolution (LTE)’s Physical Random Access Channel (PRACH), which was originally intended to be used for initial access or area tracking by a terminal (User Equipment (UE)) that is not connected to the base station, for uplink synchronization of a UE that is connected to eNodeB, when a connected UE has to transmit uplink data or to acknowledge received data or when a UE needs to perform a handoff to the target cell [2]
We have presented an IEEE 802.15.6-based overlay network that allows the LTE network to support massive M2M traffic with priorities over PRACH
Summary
In many smart city application scenarios—from building monitoring and healthcare monitoring, through smart parking and smart city lighting, to crowd sensing and vehicular safety applications—a large number of smart devices send their messages to appropriate servers for further analysis and actions, as Figure 1 schematically shows. In some M2M scenarios, messages arrive regularly with approximately constant inter-arrival times and can be transmitted using some kind of scheduled access; this is the case, for example, for healthcare applications, building monitoring and smart city lighting In other cases such as crowd sensing and vehicular safety, messages arrive randomly and may be serviced through contention-based access. Using an accurate characterization of noise and interference caused by other calls from the given cell, as well as from the surrounding cells (which is absent from other proposals), we show that the scheme is capable of achieving satisfactory performance, as well as sufficient differentiation between traffic classes It is, suitable for the massive Machine-Type Communications (mMTC) scenario—i.e., a large number of MTC devices with short messages and low arrival rates—which represents one of the major use cases for the development of 5G radio and network technology [14].
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