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Sequans Communications is enabling the second transmitter in its mobile station semiconductor products to boost Mobile WiMAX system performance. As the only WIMAX chipmaker providing two transmitters in its complete mobile device product line, Sequans is able to apply MIMO techniques in the uplink in addition to the downlink.

“The benefits of uplink MIMO cannot be ignored,” says Georges Karam, Sequans CEO. “WIMAX network operators’ recent experiences show that, as in other wireless networks, coverage is limited by the uplink. With the diversity introduced by uplink MIMO, up to a 50 percent reduction in infrastructure costs can be achieved with very little incremental cost to the mobile device and no incremental cost at the base station.”

Through the use of a novel technique called “tile switched diversity” (TSD), Sequans can bring the benefits of uplink MIMO to any Mobile WIMAX network, regardless of the base station used. Further gains can be achieved if an uplink MIMO receiver is implemented at the base station.

The benefits of uplink MIMO can be applied either to extend the cell coverage or reduce the power consumption and cost of the mobile device.

With uplink MIMO, the resultant diversity and combining gains can nearly double the cell coverage area and hence reduce network infrastructure costs by up to 50 percent.

Alternatively, uplink MIMO allows the replacement of a single transmitter and its higher output power amplifier with a dual transmitter and two 5 or 6 dB lower output power amplifiers, significantly reducing the total power consumption of the device -- a key objective in the manufacture of mobile devices. For example, in fixed gateways and modems, replacement of a single 28 dBm power amplifier with two smaller 23 dBm power amplifiers reduces total power consumption of the device by up to 750 mW, resolving thermal issues, eliminating the need for heat sinks, and therefore lowering the overall cost of the device.

“Uplink MIMO is pretty much a free benefit, squeezing the most efficiency possible out of WiMAX networks with little to no incremental cost,” added Karam. “Why would anyone not want to take advantage of it?”

Uplink MIMO is implemented in all of Sequans’ mobile WIMAX solutions, including the SQN1130 baseband mobile station chip, the SQN1140 and SQN1145 mobile station RF chips, the SQN1170 integrated baseband/RF/SDRAM mobile station chip, and the SQN2130 baseband base station chip.