Wireless communications apparatus

Abstract

MIMO UWB Communications apparatus is configured to send out a channel estimation sequence comprising a plurality of sequentially transmitted symbols in accordance with a first band hopping sequence, sent from one antenna of the apparatus, while another antenna is transmitting another sequence of channel estimation symbols in accordance with another, complementary band hopping sequence. A legacy device will be capable of synchronising with the channel estimation symbols sent in accordance with the first band hopping sequence, while a MIMO receiver will be able to determine channel estimates for all MIMO channels on the basis of the combined channel estimation transmissions.

1 . Communications apparatus comprising a plurality of antennas suitable for establishing a wideband MIMO communications channel with another communications apparatus, said wideband MIMO communications channel having at least two subbands defined therein with respect to frequency, the communications apparatus being operable to transmit from each of said antennas a signal within one or more of said subbands defined in said channel, comprising channel estimation sequence transmission means operable to cause transmission of a signal representing a channel estimation sequence for use by a receiver in estimating the MIMO communications channel, the channel estimation sequence being modulated onto a plurality of band portions defined in said wideband communications channel, the channel estimation sequence transmission means being operable to transmit said channel estimation sequence from one of said antennas by way of a band hopping sequence between two or more of said subbands, and to transmit said channel estimation sequence from another of said antennas by way of a second, complementary band hopping sequence between two or more of said subbands. 
     
     
         2 . Apparatus in accordance with  claim 1  wherein the channel estimation sequence transmission means is operable to transmit a channel estimation sequence comprising a plurality of OFDM symbols. 
     
     
         3 . Apparatus in accordance with  claim 1  wherein the channel estimation sequence transmission means is operable to transmit a channel estimation sequence comprising six OFDM symbols. 
     
     
         4 . Apparatus in accordance with  claim 3  comprising three transmit antennas and said channel estimation sequence transmission means is operable to transmit in parallel on all three antennas over six OFDM symbol periods. 
     
     
         5 . Method of transmitting channel estimation sequences in a wideband MIMO system, comprising transmitting from a first antenna a sequence of channel estimation symbols in accordance with a first band hopping sequence defined for the channel, transmitting from a second antenna a sequence of channel estimation symbols in accordance with a second band hopping sequence defined for the channel, the second band hopping sequence being complementary with the first band hopping sequence so as to avoid simultaneous transmission of a channel estimation symbol from two antennas in the same band. 
     
     
         6 . Method in accordance with  claim 5  wherein the first band hopping sequence is compatible with existing equipment to enable a SISO receiver equipped with the band hopping sequence to successfully receive the channel estimation symbols as if transmitted from a single antenna device. 
     
     
         7 . Signal transmitted in accordance with the method of  claim 5  or  claim 6 . 
     
     
         8 . Communications apparatus suitable for use with apparatus in accordance with  claim 1 , wherein said apparatus comprises a plurality of receive antennas, suitable for resolving a multiple antenna transmitted signal, channel estimation sequence detection means for detecting in accordance with a first band hopping sequence a channel estimation sequence and, in accordance with a second, complementary, band hopping sequence, a second channel estimation sequence. 
     
     
         9 . Communications apparatus in accordance with  claim 8  wherein said channel estimation sequence detection means is operable to detect a third channel estimation sequence in accordance with a third, additionally complementary, band hopping sequence.