MIMO Transmission schemes for LTE and HSPA Networks, 3G

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NOTE:Implementation complexity refers to integrated antennas for a multi-band handheld mobile deviceFigure 7. Antenna Complexity and Frequency BandAs the antennas become closer in small, handheld-form-factor devices, coupling becomes greater andantenna patterns begin to distort. As coupling increases, antenna efficiencies decrease and correlation isimpacted. Correlation must be considered in more than one context. There is the normal path correlation thatcan be determined by decompositions of the estimated channel. Also, there is antenna correlation which addsto the problem. As antennas become closer the antenna correlation tends to increase. These effects are oftencombated with forms of diversity that will be discussed in below. A summary of the challenges for variousnetwork/channel conditions is given in Table 1 below.Table 1: Summary of UE Challenges in UE-MIMO ImplementationsNetwork ScenarioRelat iveDifficultyDevice Antenna ParametersPractical Effects on theMobile DeviceInterference Mitigation ininterference limited scenarioswith strong to medium signallevels.Low• Envelope Correlation < 0.7• Antenna BPD in the range of10dB (quite “loose”)Small increase in antennavolume in device (e.g. ~ 10-25 %). Diversity antennadoes not have to performnearly as well as the “mainantenna”MIMO usage in strong tomedium signal levelenvironments.Medium /High• Envelope Correlation < 0.3 forgood MIMO “gain”• Envelope Correlation < 0.5 inworst case• “Medium” to low “BPD” isrequiredDifficult to implement inlow (< 1 GHz bands) insmall handheld devices.Device antenna volumeincrease from ~ 30% -100%SNR improvements in noiselimitedweak signalenvironments (e.g. rangeextension).High• Low BPD is needed (ideally 0dB) – the main and diversityantennas need to have the sameperformanceDevice antenna volumedoubles. Diversity antennaperformance gets closer tothat of the main antenna.BPD: See terminology section16
Mobile devices are filled with electronics, a large battery, displays and multiple antennas to support theseveral radios contained in size. These create additional coupling problems and, hence, efficiencydegradations. The problem may only get worse as the number of radios supported continues to grow. Notonly does the mobile antenna designer have to worry about GPS, Bluetooth and WiFi, he/she has to contendwith the multiple bands and even radio technologies that are needed to support wide area network cellularcommunications.Finally, the antenna designer must comply with regulations regarding specific absorption rate (SAR) andhearing aid compatibility (HAC) compliance. Given that coupling distorts the antenna patterns, thedirectionality of the resulting pattern(s) can have a direct impact on SAR and HAC.3.3.2 IMPACT OF MULTIPLE ANTENNAS ON SIZEThe impact of multiple antennas on coupling and correlation has been considered. Size is also a majorconsideration. If we focus on the 700 MHz band for a moment and note that the dimensions of an antenna isinversely proportional its frequency operation. It is easy to calculate that a length of a quarter of wavelengthmonopole antenna to be approximately 11 cm. This would be longer than many handhelds on the marketnow.Now add the fact that there will be more than one of these antennas for a MIMO application, it is easy to seethat there will be pressure to increase the size of the devices. A 700 MHz MIMO implementation couldincrease the form factor volume by up to 30% depending on the reference device (without MIMO) selected forcomparison. However, if marketing holds sway, the designer will have to sacrifice efficiency and correlationfor size. This must be accounted for in a link budget analysis to make sure that the efficiency losses do notoverwhelm the gains that you would receive by using the more propagation friendly 700 MHz band. Finally,the impact on handheld device size worsens as the number of frequency bands supporting MIMO increases.3.3.3 BATTERY CONSUMPTION OF MULTIPLE ANTENNASIncreased battery consumption is another factor in assessing the cost/benefit of multiple antennas in mobiledevices. Each antenna in a multi-antenna implementation requires dedicated components, resulting inseparate RF processing chains. These chains and components require energy to operate, which increasesbattery consumption. For example, in a simple receiver diversity implementation, battery consumption canincrease up to 25%. This increase in battery consumption would also be expected in MIMO implementations.This condition worsens as the number of frequency bands supporting MIMO increases. Also in the context ofRx diversity, the impact on current consumption is different for the coverage versus capacity case.17
Page 2 and 3: Table of Contents1 TERMINOLOGY ....
Page 4 and 5: 1 TERMINOLOGYIt is assumed that the
Page 6 and 7: 3 PRINCIPLES3.1 MULTI‐ANTENNA‐T
Page 8 and 9: 3.1.3 PEAK RATE OR COVERAGEIn a cel
Page 10 and 11: sufficiently accurate channel infor
Page 12 and 13: Figure 5. Examples of Power Delay P
Page 14 and 15: 3.2 BS ANTENNA CONFIGURATIONSFigure
Page 18 and 19: 3.3.4 ADVANCED‐ANTENNA CONCEPTS F
Page 20 and 21: and interference. By considering th
Page 22 and 23: ank over all the feasible 1 set of
Page 24 and 25: Typically a constant delay increase
Page 26 and 27: the columns of Λ U r rxrfor some o
Page 28 and 29: to blindly estimate this power rati
Page 30 and 31: Figure 16. MMSE Receiver for UL MU-
Page 32: transmitter has information about t
Page 35 and 36: Intra-site CoMPBS3BS2Inter-site CoM
Page 37 and 38: 5.5.4 UL COMPUplink coordinated mul
Page 39 and 40: 6.2 DL SYSTEM PERFORMANCE6.2.1 THE
Page 41 and 42: Compared to baseline, SE gains for
Page 43 and 44: 6.2.3. CL‐MIMO WITH DIV ANTENNA C
Page 45 and 46: 6.2.4. MIMO WITH ULA‐4VWith the U
Page 47 and 48: 0.035Baseline Uplink Cell Edge Sect
Page 49 and 50: 7 CONCLUDING REMARKSThis report pro

MIMO Transmission schemes for LTE and HSPA Networks, 3G

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