the existing 850 band adding 10 MHz at the lower end of the present Band V allocation to provide a 35-MHz rather than a 25-MHz pass band. Band performance relative to Band V would be degraded by about 1 dB. The bands made available by the digital switch over at 700 MHz in the USA and 800 MHz in Europe have also introduced particular challenges, which we review in Chapter 5. On the 28 June 2010, the US Obama administration issued a memorandum stating an intention to auction a further 500 MHz of spectrum over and above present allocations. Some but not all of this will line up with rest of the world band plans and may or may not include spectrum in L band at 1.4, 1.5 and 1.6 GHz and S band allocations presently ring fenced for hybrid satellite/terrestrial networks. Additionally in some form factors, for example tablets, slates and lap tops, there may be a future need to integrate ATSC TV receive and/or DVB T2 receiver functionality in the 700- MHz band for portable rather than mobile reception. This receive capability has to coexist with locally generated frequency duplexed (FDD) and time-domain duplexed (TDD) transmit energy. 4.3.1 FDD versus TDD At this point a short digression into the relative merits of FDD and TDD is needed. A traditional FDD duplex band plan is shown in Table 4.4. The duplex gap in a cellu- lar/mobile broadband handset keeps the TX power from one set of users getting in to the Table 4.2 Band allocations and duplex spacing Allocation Duplex Band 3GPP (MHz) Uplink spacing (MHz) Downlink Region 2 X 60 1920-1980 2110-2170 Present UMTS 2 X 60 1850-1910 1930-1990 US PCS 2 X 75 1710-1785 1805-1880 GSM Europe, Asia, Brazil 1700/2100 2 X 45 1710-1755 2110-2155 New US 2 X 25 824-849 869-894 US and Asia 2 X 10 830-840 875-885 Japan 2 X 70 2500-2570 2620-2690 2 X 35 880-915 925-960 Europe and Asia 2 X 35 1750-1785 1845-1880 Japan Making Telecoms Work Table 4.3 Twenty-five band allocations Uplink Downlink Duplex 1749.9 1784.9 1844.9 1879.9 1427.9 1452.9 1475.9 1500.9 receive band of another set of users. 