MIMO is an attractive enhancement to 3G HSPA networks, although it has not been widely deployed. The objective of this paper is to discuss an applicability of MIMO technique in HSPA networks with supplementary use of VAM feature enabling smooth coexistence with non-MIMO HSDPA users. Observations performed on live network show that MIMO deployment costs can be reduced with gradual rollout prioritizing cells with upgraded PA to 2x20W and re-utilizing antenna lines. 1. MOTIVATION According to GSA (Global mobile Supplier Association) nearly 70% of 3G operators have launched HSPA+ (High Speed Packet Access) with DC-HSPA (Dual Cell- HSPA) as a 3G evolution mainstream . At the same time market research indicate that MIMO (Multiple Input Multiple Output) technique despite of being one of the key technologies for LTE (Long Term Evolution) and WiMax networks, it has not been widely deployed in HSPA+ networks  . This fact has been often commented as an unavailability of HSPA MIMO-capable terminals on a mass market, need for the second pilot SCPICH (Secondary-Common Pilot Channel) reducing code and power performance, and considerable roll out CAPEX (Capital Expenditure). Moreover, some reports indicate that transmit diversity transmission mode - STTD (Space Time Transmit Diversity) in 3G , may degrade performance of regular non-MIMO HSPA users ,. In this paper, HSPA RAN (Radio Access Network) enhancement through MIMO introduction together with VAM (Virtual Antenna Mapping) is studied, and accordingly, an applicability is analyzed based on audit performed on a commercial 3G network. 2. MIMO in HSPA MIMO 2x2 (i.e. with two transmit and receive antennas) for HSDPA has been introduced in Rel. 7 3GPP (Third Generation Partnership project) specification ,. Two MIMO transmission modes have been defined - a single (also called as transmit diversity) and a dual layer (also called spatial multiplexing) mode. With a s[...]
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