Telecoms, Datacoms, Wireless, IoT


The heart of M2M technologies - the evolution from GSM to GPRS, EDGE and HSDPA

16 May 2007 Telecoms, Datacoms, Wireless, IoT

In 1995, a group of engineers at Siemens answered a classic question through a surprisingly simple, yet extremely effective idea: ‘what would happen if we took out the component that establishes the radio connection in a mobile phone and made it available for other applications?’

The pioneer of radio modules that shipped independently of a mobile phone was called the M1: it consists primarily of a circuit board which combines the baseband processor, transmitter (referred to as the HF part), power supply controller and memory. That is all that is needed for an elegant exchange of data across GSM networks.

Bandwidth increase drives innovation

The big innovation for the M2M (machine-to-machine) market was the first radio module, which paved the way for the evolution of the mobile communications industry. For a long time after that, new discoveries from module manufacturers followed the innovations in the mobile communications world. And so, most developments had their origins in the constant expansion to other frequency ranges, known as bands, through new mobile telecommunications operators.

The European Conference of Postal and Telecommunications (CEPT), a standardisation body consisting of European postal authorities, started it all in the mid-eighties by reserving the GSM 900 frequency band 890 to 915 (uplink) and 935 to 960 MHz (downlink) for mobile communications. From this, the so-called D network evolved in the early '90s.

When the market began to boom, new operators entered it. The regulatory authorities gave them an additional high-frequency band, GSM 1800, also known as the E network (1710-1785 MHz for the uplink and 1805-1880 MHz for the downlink). To operate in both frequency bands, dual-band radio modules were needed. This was the precursor to the birth of the first dual-band radio modules such as the TC35 from Siemens.

Parallel to the addition of a new band, the radio modules kept getting smaller. Radio modules shrank at the same rate as processors, memory, and interfaces. Thanks to the high level of integration, they are now smaller than a box of matches.

Since the radio modules were planned to be used around the globe, the next logical step was to incorporate the frequency band used for mobile communications in the US, GSM 1900. This was made possible by developing corresponding tri-band radio modules capable of operating on any of the three frequency bands. Since the new GSM 850 (850 MHz) frequency band has been available, the latest evolutionary step is the quad-band module.

GPRS opens a slot in time

When GPRS, (general packet radio service), was introduced, the speed of wireless data transmission increased dramatically. In contrast to the HSCSD Technology (high speed circuit switched data) used in the past, GPRS uses multiple radio slots simultaneously (multislot technology) to reach transmission rates of up to 171 Kbps. Similar to the TCP/IP protocol, GPRS is based on the transmission of individual data packets and does not send a continuous stream of data.

The packet-based data transmission is particularly useful for M2M applications such as POS terminals or alarm systems that transmit images as well as gateways or GPRS PCMCIA cards. Thanks to GPRS, users can stay connected to the Internet all day without incurring high fees since GPRS service is not billed by the amount of time spent online, but rather by the amount of data transmitted.

Radio modules such as the MC55, TC63 and TC65 from Siemens are no longer limited to just GPRS. They now also support packet broadcast control channel, or PBCCH. The new PBCCH signal channel improves transmission capacities in GPRS networks. This means that the resources of wireless network providers can be optimally utilised in data transmission.

Enhanced data rates for GSM evolution (EDGE) is an enhancement of the GPRS technology. EDGE provides improved performance for wireless data using a faster modulation method over the existing GSM standard (8-PSK/phase shift keying). Transfer rates of up to 472 Kbps can be attained. EDGE is the last intermediate step before UMTS wireless data and has already been implemented by Siemens in the MC75 radio module.

Open platform

One of the most important innovations in M2M technology in recent times was the open platform support of wireless modules. An M2M application that is connected to an electricity meter or a POS terminal consists of ordinary computer components in addition to the wireless terminal. That includes items such as the CPU, ROM, RAM, and interfaces for I/O peripherals and specialised software. Now, all the components named above, with the exception of the software, are already included in the module. With open platform, developers can use the components for their own applications. For the TC65 radio module from Siemens, this is accomplished with the widely available Java platform J2ME (Java 2 Micro Edition). This saves both costs on materials, and by using the components that have already been integrated in the module. The cost of integrating and testing hardware and software is also reduced for application developers. This allows companies to go-to-market faster and with a smaller budget.

In addition, an important feature offered by the Java Open platform is the support of OTAP (over the air provisioning) which allows the developer to upgrade his Java application in the wireless module remotely from a central server over GSM/GPRS/EDGE. This offers enormous flexibility and cost benefits in large-scale installations from an application code upgrade and maintenance perspective.

Common paths to wireless communications

There are now a number of different wireless data technologies. But for long distances, wireless communications based on GSM/GPRS or UMTS, play a key role. DECT (the cordless telephone standard), Bluetooth, and W-LAN all operate over short distances. Only when they are combined with a GSM/GPRS/UMTS module do they have what it takes to go the distance for long-range transmissions.

The SIM Access Profile (SAP) technology for automotive applications demonstrates how Bluetooth and GSM/GPRS can be effectively combined. SAP gives all voice and Telematics services, within the vehicle wireless access via Bluetooth to the information on the mobile phone SIM card without the driver needing to remove the SIM or obtain a second card. The AC45 from Siemens was the first module to feature this technology but it is now available on most Siemens modules.

Additional solutions that show how wireless technologies can be combined, are the XT65/75 radio modules from Siemens, which combine GSM/GPRS/EDGE technology with GPS technology. This combination of wireless communications and satellite tracking enables a wide range of tracking solutions in applications such as fleet management, vehicle tracking, navigation, emergency calling, and location-based services. The modules can, for instance, make the transportation of valuable cargo more secure by continually transmitting positioning data on the location of the cargo to the owner and the transport company via GSM/GPRS/EDGE.

The next step in the evolution of radio module technology is HSPA (high speed packet access) technology which is a collection of mobile telephony protocols based on the UMTS technology. Currently, HSDPA (high speed downlink packet access) and HSUPA (high speed uplink packet access) standards have been established and a third standard HSOPA (high speed OFDM packet access) is being developed. The obstacle in supporting HSPA protocols in countries running GSM networks is that the existing GSM equipment cannot be used. Hence new radio towers and network upgrades are required in order to support the technology. These network upgrades are currently underway with many countries already supporting HSDPA at 3,6 Mbps. As a result of its speed, HSDPA offers new services for end users such as live streaming of video and music, high-speed downloads, broadband Internet access, and interactive games. The newly launched HC15/25 modules from Siemens are the first to support HSDPA at 3,6 Mbps. The modules also support EDGE and GPRS as a fall-back for when used in areas that do not yet support HSDPA.

Looking ahead, the next generations of HSDPA will support 7,2 Mbps and 14 Mbps data rates with some networks planning to be ready for this before the end of 2007. HSUPA provides an improvement in the uplink performance and supports a maximum data rate of 5,6 Mbps. This technology will most likely find use in remote monitoring and security applications where video needs to be streamed 'up' from a remote site. HSOPA, often referred to as Super 3G is positioned to eventually replace HSDPA and HSUPA and will provide downlink speeds of up to 100 Mbps and uplink speeds of 50 Mbps. As soon as the basic infrastructure is available, there will also be M2M radio modules for these high speed HSPA networks - the height of evolutionary achievement in radio modules.

For more information contact Siemens Southern Africa, +27 (0)11 652 2000.





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