Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

3GPP Long Term Evolution (LTE) 219HSPA is the OFDM downlink and single-carrier FDMA uplink. LTE is targeting datarates of 100 Mbit/s in the downlink and 50 Mbit/s in the uplink. The improvements indata rate are due to enhanced channel-dependent scheduling and rate adaptation, also inthe frequency domain, spatial multiplexing with MIMO, and larger channel bandwidthsof up to 20 MHz.4G (IMT-Advanced)The fourth generation (4G) of the cellular mobile radio is referred to as IMT-Advancedand encompasses new radio technologies as well as existing technologies. The standardizationof new physical air interfaces is targeting downlink peak data rates of 1 Gbit/s atlow mobility and 100 Mbit/s at high mobility.5.2.2 Requirements on LTEThe LTE radio access technology should be optimized for packet switched traffic withhigh data rate and low latency. The requirements that have to be fulfilled by LTE aredefined in Reference [5] and summarized in Table 5-2.With the figures from Table 5-2, the expected achievable spectrum efficiency in thedownlink results in 5 bit/s/Hz with 100 Mbit/s in the 20 MHz bandwidth and correspondinglyin 2.5 bit/s/Hz with 50 Mbit/s in the 20 MHz bandwidth in the uplink. The LTEperformance presented in Section 5.2.11 shows that the LTE specification R8 exceedsthese required spectrum efficiencies.Table 5-2 Requirements for LTE [5]ParameterPeak data ratesAverage user throughput per MHzcompared to HSPA Release 6Spectrum efficiency in bit/s/Hz/cellcompared to HSPA Release 6MobilitySupported bandwidthsSpectrum allocationLatencyNumber of users per cellTarget figures100 Mbit/s for downlink50 Mbit/s for uplink3–4 times higher for downlink2–3 times higher for uplink3–4 times higher for downlink2–3 times higher for uplink0–15 km/h (optimized for this range)15–120 km/h (high performance guaranteed)120–350 km/h (connection maintained)1.25–20 MHzOperation in paired spectrum (FDD) andunpaired spectrum (TDD) should be supported5 ms user-plane latency at IP layer, for one-way100 ms control-plane latency from idle toactive stateAt least 200 at 5 MHz bandwidthAt least 400 at bandwidth higher than 5 MHz