Network test system can emulate tens of thousands of M2M devices
The TM500 can evaluate the effect on the network of connecting large numbers of low-power, low-complexity UEs (user equipment) for MTC applications. Using cellular networks to connect MTC devices offers the benefit of wide area coverage on an existing stable network. Non-speech devices that will use MTC will include smart meters, security cameras, environmental sensors, and a whole range of industrial and commercial sensors and controllers. Unlike mobile phones, MTC devices need to have an extended battery life of up to ten years, low unit cost, and a low cost of deployment.
“The main driver for MTC is the widely-publicised forecast that LTE networks will be used to support the development of the Internet of Things,” said Phil Medd, Senior Technical Product Manager at Cobham Wireless. “With billions of non-speech devices expected to be connected over the next 10 years, it is crucial that network operators can optimise the current 4G networks to connect them, rather than needing to wait for the promised 5G capacity increase.”
TM500 is an established network test platform, that validates networks under realistic usage and loading scenarios; this updates adds new 3GPP features enabling the TM500 – Cobham says – to stay ahead of market need, empowering network operators to prove network performance under real-life usage conditions before the availability of actual device hardware.
Cobham Wireless; www.cobham.com/wireless
Next page; Cobham provides a quick guide to 3GPP advances relevant to M2M/IoT traffic…
LTE Cat-0 and LTE-M
LTE Cat-0 is a protocol that was introduced at 3GPP Release 12, and makes provision for simplified UEs for MTC applications. Cat-0 reduces the complexity of the UE and modem by using a single receiver RF path, with a single antenna and reduced throughput down to 1 Mbps, as well as a smaller transport block size and mandatory half-duplex mode support. It also has a power saving mode (PSM) that enables the UE to enter a low power state for up to approximately 12.9 days, during which it cannot be paged by the network.
With Release 13 a new category has been introduced that is more precisely optimised for the requirements of MTC. LTE-M, which is also known as Cat-M or eMTC, allows the Bill of Materials (BoM) to be lowered due to the use of a single receive chain and reduced transport block size. Operating in half-duplex mode, the standard channel bandwidth is reduced to 1.4 MHz, carrying six physical resource blocks (PRBs), which can be used within the system bandwidth of an existing network. Multiple blocks of six PRBs can be deployed across the system bandwidth, so for example a 20MHz LTE band can support up to 16 sets of Cat-M channels, thus increasing the capacity of the network.
Cat-M also offers reduced power consumption, allowing the device designer a choice between implementing a PSM or an extended DRX (eDRX) cycle, which allows a device in idle mode to deactivate its receiver for longer than the current 2.56 seconds, while still reachable by the network.
Coverage enhancements have also been introduced in Cat M. These can extend the range of a cell or improve signal penetration into buildings, as many MTC devices will be located indoors. There are two coverage enhancement modes, CE Mode A and CE Mode B, providing up to 15 dB enhancement using a variety of techniques such as subframe repetition, frequency hopping, boosting the reference symbols, and enhanced PRACH (Physical Random Access Channel), as well as increasing transmit power.
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