ple in pico- or femtocells in terms of impact on application performance and user experience value then it would seem that optimising SISO antenna performance should be a priority over and above MIMO optimisation. Presently this would not appear to be the case. It is particularly important to ensure that an overaggressive pursuit of peak data rates in small cells does not compromise average data throughput in larger cells. A MIMO antenna design ideally needs to deliver a net gain in a wide range of operational conditions. This is often not the case. 5.6.5 MIMO Testing MIMO OTA standardisation started in the CTIA and later the 3GPP standards process. The rather complex relationship between MIMO antenna performance, spatial channel gain and scheduling efficiency makes it difficult to agree on an objective figure of merit that captures real-life conditions and real-life throughput performance. 29 Future multiplayer gaming devices being one example. 30 See also CTIA/PTRCB test procedures for the US market http://www.cetecom.com/us/en/certification/north- america/ctia/over-the-air-performance.html, The test procedures state a requirement of a minimum of 50% antenna efficiency. Optimum antenna designs can approach 70% efficiency (measured in an anechoic chamber). Some handsets shipped in to some markets have been measured at 10% efficiency, which would appear to validate the need for a minimum acceptable performance threshold to be applied in all markets. Orange, 'OTA TRP and TRS requirements for GSM 900 and 1800', 3GPP R4-091762. Making Telecoms Work One approach is to undertake SISO measurements and then emulate arbitrarily complex spatial channel conditions and frequency selective scheduling gain. MIMO gain relative to SISO is dependent on low antenna correlation and high signal-to-noise ratios. Low antenna correlation is more likely to be achieved at higher frequencies. Such gains are only likely to be significant in cells where the Doppler speed and channel conditions change slowly enough to allow adaptive modulat