Trong phần sau đây, mỗi đoạn bắt đầu với một tham chiếu trực tiếp để yêu cầu được đưa ra trong đó. MIMO đề nghị đó sẽ được toàn diện bao gồm các kỹ thuật cho một, hai và bốn ăng-ten ở trạm cơ sở và UE. | Coverage and Capacity Enhancement Methods 363 In the following each paragraph begins with a direct reference to requirements given therein. MIMO proposals shall be comprehensive to include techniques for one two and four antennas at both the base station and UE. This requirement is motivated by the fact that deploying multiple antennas in the mobile terminal or BS to support MIMO techniques is not straightforward due to concerns of cost complexity and visual impact. This is especially true of today s mobile terminals where basic products with large production volumes may have at most two antennas. Multi-mode terminals supporting for example WCDMA GSM and GPS may already require several antennas even without applying MIMO processing. Macro-BSs typically employ two or four antennas and it is expected that two-antenna BSs will dominate in number in the near future. Thus in practice mobile terminals and data modems may have four antennas at the maximum while two antennas represent the most likely solution. For each proposal the transmission techniques for the range of data rates from low to high SIR shall be evaluated. This is a trivial but important requirement since the gain from information MIMO greatly depends on the SIR SNR as is seen from Figure . Especially in macro-cell environments the operating SIR SNR in HSDPA is most of the time less than 10 dB and the practical performance differences between various diversity MIMO and information MIMO techniques need not to be as large as Figure hints. Operation of MIMO technique shall be specified under a range of realistic conditions. The conclusion drawn from this requirement is that there should be realistic channel models for simulations. This topic has been considered in 24 . Moreover to imitate realistic conditions implementation non-idealities should also be taken into account. The MIMO technique shall have no significant negative impact on features available in earlier releases. Let us give an example of
