How mobile comms instrumentation is meeting the big data and IoT challenge
It is 25 years since the 900 MHz GSM standard marked the birth of digital wireless communications. The hunger for data in cellular communications remains insatiable and demand for further technological progress persists. A tenfold increase in mobile data traffic is expected over the next six years, and experts predict an exponential increase in the number of things (Internet of Things, IoT) that communicate with each other via mobile networks. Inexorable growth in the both the number of subscribers – and the amount of data they consume - means mobile network operators need to guarantee an excellent quality of experience long into in the future.
2G/3G/4G technologies and future improvements
State‑of‑the‑art, commercially available LTE‑A devices achieve 600 Mbit/s in ideal lab environments. In real networks, propagation conditions and the shared channel principle reduce achievable download speeds due to the fact that available bandwidth is divided among all active subscribers. Nonetheless, LTE / LTE‑A technology has significantly enhanced available data rates and network capacity. There are a number of reasons for this.
- A wide system bandwidth of 20 MHz that can be provided to an individual subscriber as well as the ability to bundle up to five of these 20 MHz carrier frequencies for each subscriber (commonly known as carrier aggregation, CA).
- Use of spatial multiplexing (MIMO technology), i.e. using from two to eight/four transmit/receive antennas.
- Fast OFDMA multiplexing enables the frequency and time resource allocation to be changed on a millisecond basis.
- High‑quality modulation methods, specifically QPSK, 16QAM, 64QAM and 256QAM.
Meeting demands by measuring against standards
Introducing LTE / LTE‑A has allowed network operators to meet increasing demands. Several key LTE improvements have resulted from enhancements introduced by the 3GPP standardization body. Examples include:
LTE’s enhanced multimedia broadcast multicast service provides a highly efficient method of addressing mobile TV applications, for example, where many subscribers receive the same data simultaneously. This mode also allows wireless devices to install new software efficiently without requiring individual data connections for each device.
3GPP specifications provide a special mode to use, for example, an email application running in the background via WLAN while transmitting video data via LTE. Alternatively, operating LTE / LTE-A in unlicensed frequency bands allows data rate capability to be increased using the carrier aggregation feature. Also combining data on IP layer from both LTE / LTE-A in licensed and WLAN in unlicensed spectrum is possible.
RF and protocol testing systems help network operators select suitable wireless device providers. The test solutions ensure that the devices comply with mobile network standards. Picture credit: Rohde & Schwarz
In heterogeneous networks such as pedestrian areas of cities, coordinated multipoint transmission and reception (CoMP) makes it possible to transmit a signal to a wireless device in a coordinated manner. Using MIMO technology and also influencing the baseband signal (precoding) in a coordinated manner allows optimal coverage at cell boundaries.
The introduction of device‑to‑device (D2D) capabilities is of special importance, as these provide two fundamental new functions. First, the network-supported discovery function makes it possible for two spatially neighbouring wireless devices to detect each other. Secondly, these devices and others in their vicinity will be able to exchange data directly, i.e. without going through the base station covering the area. In this case data is broadcasted to a number of potential interested users in the vicinity or point to point communication takes place. The latter part of the technology is limited to public safety and security applications. . However, it could be extended, for example to support automotive applications including autonomous driving in the future.
Even though LTE / LTE‑A networks demonstrate increasing performance, comprehensive 4G coverage will take time. Efficient handover to 2G and 3G technologies remains critical. There are also many cases where 2G / 3G data rates are sufficient and a low-tech approach allows cost-efficient solutions with long battery life. For example, modules with GPRS technology are often used in machine‑to‑machine (M2M) environments.
The high performance of LTE / LTE-A technology, its seamless cooperation with existing 2G / 3G networks and the complementary use of WLAN enable network operators to meet subscribers’ continuously growing big data requirements. Broadcast / multicast solutions enhance system flexibility.
LTE /LTE‑A has already ushered in several improvements to serve M2M applications. For example, there is a category 0 for LTE user equipment that reduces the effort required to implement this class of devices (lower data rate requirements and no MIMO support). Processes have also been introduced to prevent mobile network overloading when large numbers of M2M devices attempt to access the network simultaneously. Progressing this path, latest improvements include a reduction of bandwidth as low as 180kHz with reduced mobility support. Effectively an M2M optimised radio access technology (RAT) was added, which uses LTE parameters and procedures only as far as required for this specific use case.
Cost‑efficient mobile T&M equipment is used to install a base station. Picture credit: Rohde & Schwarz
The increasing number of things communicating with each other in the future (IoT) and new demands stemming from vertical branches of industry (automotive industry, health care, robot control, etc.) are expected to dictate further significant enhancements. That is why researchers in the mobile communications industry are already designing and evaluating 5G as they look toward 2020 and beyond. Instrument vendors such as Rohde & Schwarz and its subsidiaries SwissQual and ipoque offer a comprehensive portfolio for today’s T&M tasks and are actively involved in 5G research and development.
How does T&M equipment contribute?
Test and measurement equipment plays a central role in both introducing new technologies and in operating networks. Countless test solutions are required to develop and manufacture mobile devices, components, base stations and switching nodes. Test solutions are also needed when deploying the network and verifying its performance.
Network operators have to select the right infrastructure products to operate their networks. Using instruments such as signal generators and signal and spectrum analysers, they can qualify infrastructure products to select those that perform best. Many operators specify additional tests based on their specific network requirements. T&M equipment such as the R&S®CMW500 wideband radio communication tester emulates all required network functions; verifying whether a wireless device is behaving properly ensuring hardware is correctly implemented (for example, achieving specified date rate limits and complying with specified maximum transmit power).
When deploying base stations in the field, compact testers are needed to quickly verify whether regulatory requirements are being met. Following deployment, operators need to adjust parameters, such as handover thresholds, and identify coverage gaps in order to optimize their network and ensure the best possible data rates. QualiPoc from SwissQual implements a measurement application on a commercial smartphone. The test solution can be used like a normal app, enabling network operators to evaluate end user experience.
Network operators use T&M equipment to analyse network performance and optimize the end user experience. Picture credit: Rohde & Schwarz
In the operator’s core network, where all data streams are processed, it is increasingly important to be able to analyse data traffic down to the packet level. This makes it possible to classify the data traffic and optimally route a service’s data packets through the network. IP analysis technology provides this insight. The same functionality is also of great interest for mobile device testing. When implemented on the R&S®CMW500, users can analyse which IP data streams (including protocols used) a smartphone maintains only due to applications running in the background.
There can always be unforeseen interference when operating mobile networks. Stationary network monitoring tools in the mobile network and mobile interference hunting solutions are used to identify and eliminate this interference as quickly as possible. For example, malfunctioning neon signs can create interference in base station receive bands and negatively impact all data traffic in a cell.
Test instruments are also helping to delineate the next generation of standards. Already signal generators and signal analysers are used to evaluate potential 5G technology components. Test and measurement are indispensable because of their flexibility in terms of frequency range, bandwidth and transmission technology. They are also essential components of measuring systems used to analyse propagation conditions in new, undefined frequency bands. Multiport network analysers will play a decisive role in implementing future antenna technologies. To the same degree over the air test capabilities will become essential as RF connectors may no longer be accessible in cm- and mm-wave spectrum. Finally, the influence of individual applications on data rates, signalling loads and current drain are under examination. This will be especially important for IoT modules as it must be possible to measure individual applications on the IP layer itself.
In all these areas, instrumentation is evolving to ensure technology and user experience standards are maintained.
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