not work particularly well in large cells as additional time-domain guard band needs to be introduced to avoid intersymbol interference between transmit and receive time slots. TDD does not work particularly well in small cells as base stations and users within a cell radius are likely to be closer together and therefore more likely to create mutual interference. This will be particularly noticeable with more extreme duty cycles, for example when some users require uplink rather than downlink asymmetry. As a prior example of this, the three PHS networks deployed in Japan in the mid-1990s were not intersynchronised. PHS networks were also deployed in China, Taiwan and Thailand but never gained an international market footprint. This was partly due to the intersymbol interference issue but also due to the fundamental fact that TDD devices have poor sensitivity. Power in transmit devices does not disappear instantaneously and substantial residual power can still be visible within the RX time slots. This does not matter when the duty cycle is relatively light, for example in a basic GSM voice path where only one slot in eight is transmitting. It certainly matters if the TX duty cycle is high, which in many mobile broadband cases it will be and/or if high peak data rates are supported. If the asymmetry is changing rapidly over time the signalling bandwidth will also become disproportionate. So in practice, any theoretical gains available from TDD will disappear in implementation loss. TDD may provide higher headline peak data rates but the average data throughput will be lower. TDD next to a LTE FDD receive channel will also be particularly bad news both at the network level, base station to base station, and in the user equipment receive path. Given that it is unlikely that FDD will disappear for the foreseeable future, most user equipment will need to be dual mode, SO any potential component savings, eliminating duplex filters for example, would not be possible. Although the RF specifications are similar they are no