|Researchers at Nokia Siemens Networks double the capacity in uplink using Virtual MIMO in LTE networks. Reduction of user equipment cost and power consumption|
In a recent lab test, Nokia Siemens Networks, a pioneer in the continuing development of mobile communications, has shown how a Virtual Multiple Input Multiple Output (MIMO) method can be used for the uplink in LTE (Long Term Evolution) networks. Using the SDMA (Space Division Multiple Access) technique two standard mobile devices, each with only one physical transmission antenna, communicate with a base station simultaneously and on the same radio channel. Using this technique an aggregated uplink transmission speed of 108 megabits per second was achieved instead of the usual 54 megabits per second. While MIMO on the downlink primarily generates higher peak data rates for the end user, Virtual MIMO on the uplink brings benefits for the network operator by making it possible to increase network capacity and better utilize the available spectrum.
In addition, Nokia Siemens Networks also contributed to meeting one of the most important prerequisites for the market success of LTE: The LTE devices are to have acceptable power consumption requirements despite data-intensive applications and be available at moderate prices. With Virtual MIMO only one power amplifier and transmission antenna is necessary for each device, and that reduces production costs and power needs.
In late 2006 Nokia Siemens Networks became the first company to show an LTE radio network in live operation, demonstrating it at the 3GSM World Congress in Hong Kong. Using the downlink MIMO technology, it achieved a speed of 160 megabits per second from the base station to mobile device.
The researchers from Nokia Siemens Networks now proved that Virtual MIMO – which is also termed Space Division Multiple Access (SDMA) – is also possible in LTE systems. In the test bed, which was constructed in collaboration with the Fraunhofer Institute for Telecommunications (Heinrich Hertz Institute), two cooperating wireless end-user devices form a Virtual MIMO system in which the antenna elements are distributed over the two devices. The two devices can be supplied simultaneously with data over the same frequency band using space division multiplexing. During the demonstration, an HDTV (high-definition television) broadcast was transmitted at the same time in the uplink and downlink direction. In parallel, a random data sequence was sent from and to the second device. The total data rate was 108 megabits per second (uplink) and 160 megabits per second (downlink).
“An important aspect of future wireless systems is less cost and complexity, coupled with optimum use of existing frequency bands,” said Stephan Scholz, CTO at Nokia Siemens Networks. “Our experimental system enabled us to demonstrate the feasibility and great advantage of SDMA for future wireless systems and specifically for LTE. As a result, we have obtained another important module for LTE and demonstrated the considerable potential of this standard.”