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THE ORIGINAL PUSH-PULL CONNECTOR additional spectrum resources. given the scarcity and cost of the wireless operator’s spectrum, improving the spectral effi- ciency is a critical goal for improving the overall financial operat- ing margins for the mobile operator. it is important to note that commercial MiMo systems switch dynamically between SiSo, MiMo diversity, and MiMo mul- tiplexing modes, depending on a variety of factors including the channel environment and signal quality. For example, if the signal quality is very high the system uses spatial multiplexing, and if not, it automatically switches to spatial diversity mode or even to SiSo mode. MIMO challenges the key challenge of using MiMo is that it can require more infrastructure and is therefore more expensive than using SiSo. DAS products use remote amplifier units (RAUs) to broadcast signals. Contemporary advanced RAUs can usually support one or two antennas and one or more frequency bands. thus, to do MiMo on, say, two frequency bands (i.e., 700 Mhz and 2300 Mhz) while providing SiSo service on other bands (e.g. 900MHz, 2100MHz) can require a second RAU and a second antenna to provide MiMo service on each band. In some deployments, such as low traffic areas, the operator requirement is to focus initially on providing Lte coverage over as wide an area as possible, without emphasis on MiMo, so spending extra money to deploy MiMo in DAS systems is not preferred. However, MIMO is often required for high-traffic areas such as sports arenas, convention centres, and airports, and MiMo will be deployed in these venues because it is required to deliver the necessary capacity. in addition, DAS vendors are working hard to reduce the overall cost of implementing MiMo, largely by increasing the More than capacity of RAUs so they can handle more frequency bands 50'000 connector and more antennas. combinations MIMO alternatives The modular design of MIMO increases spectral efficiency because it allows the mobile LEMO products provides operator to use two radios in the same frequency band to dou- more than 50'000 ble the network throughput over the DAS. the alternative is to different combinations use SiSo mode and double the number of radios in the system. of connectors with a However, this requires the mobile operator to use two different large choice of contact frequencies, depleting precious frequency resources. there is a configurations: new 3gPP Lte Advanced feature called carrier aggregation that uses multiple RF channels at different frequencies to trans- High and low voltage mit data simultaneously to a user. this is similar in concept to Coaxial and triaxial MiMo except that MiMo uses the same rF channel instead of Quadrax multiple RF channels. The benefit of carrier aggregation is that it does not rely on the multipath environment and should provide Thermocouple more consistent throughput, but at the cost of more spectrum. Fibre optic Another alternative is to increase the density of the modula- Fluidic and pneumatic tion scheme (i.e. higher order modulation). Most of the cellular wireless systems are using at most 64-QAM modulation with Hybrid coding. the throughput could be increased using a higher See us in Hall B4 Custom solutions Booth 273 order modulation such as 128-QAM or 256-QAM, but this would 13-16 November 2012 Cable assembly require a much cleaner channel (i.e. substantially higher SNr and less fading). in addition, the higher throughput would be limited to a smaller area surrounding the antenna. LEMO SA - Switzerland MIMO rollouts Phone: (+41 21) 695 16 00 Over the next five years or so, operators will deploy MIMO spa- Fax: (+41 21) 695 16 02 tial multiplexing mode first in high-traffic areas, typically large info@lemo.com public venues such as airports, arenas, and stadiums, where Contact your local partner onwww.lemo.com obtaining maximum capacity in the network is the primary www.electronics-eetimes.com Electronic Engineering Times Europe November 2012 39


EETE NOVEMBER 2012
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