Experimental interference assessment between two independent and simultaneous 4 x 4 MIMO handset user links , operating at 5 GHz

Though interference is well known to be a significant burden on multiple input multiple output (MIMO) communication systems, mostly signal to noise ratio (SNR) limitations have been studied, whereas little experimental interference behavioural knowledge exist in open literature so far. In this letter we present measured simultaneous signal to interference ratio (SIR) data due to realistic terminal handling. Not only is the environment changing for two separate mobile terminals but the user interaction (handling) on each mobile is also changing independently. Thus, the user interaction on the wanted terminal will impact its ability to overcome interference of another user, while at the same time the other user’s interaction on his/her terminal will influence the actual interference on the wanted terminal. Introduction and Background The measurements presented use the same data as in [1], i.e. two independent 4x4 MIMO handset users operating fully simultaneously at 5GHz while subject to three different base station (BS) links. A key metric to define, is the interference in the MIMO case. We base it on the singular value decomposition of the wanted normalised channel between a base station and mobile, which is denoted H1 and the interfering normalised channel between another base station and mobile, denoted as H2I. The same analysis can be made using H2 as the wanted channel and H1I as the interfering channel instead). In general, for channel n, singular value decomposition can be applied as follows [2]: [ ] [ ] H n H n H n H n