MIMO Transmission schemes for LTE and HSPA Networks, 3G

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codebook. The performance of unitary codebook MU-MIMO is generally worse than that of the non-unitarycodebook based MU-MIMO because the channel seen by the UE does not exactly match the unitarycodeword. This will cause inter-user interference and degrade performance. For non-unitary codebook basedMU-MIMO, the beams can be formed exactly in the direction of the UE and in the case of zero-forcingbeamforming, the set of beams that are used for the transmission can be made exactly orthogonal. However,since user specific non-unitary codebook based beams are used, a user specific reference signal is neededfor channel estimation. Although the MU-MIMO schemes discussed so far are codebook based, it should benoted that MU-MIMO schemes based upon non-codebook type feedback are also possible.For the UL, joint processing could be done on base station for MU-MIMO. The MMSESIC is the optimalscheme to reach MU-MIMO upper-capacity regions. Furthermore, recent advances in optimization procedureshave shown that numerical efficient implementation of this scheme may now be possible.5.5 CoMPCoordinated multi-point transmission/reception (CoMP) is considered by 3GPP as a tool to improvecoverage, cell-edge throughput, and/or system efficiency.5.5.1 PRINCIPLEThe main idea of CoMP is as follows. When an UE is in the cell-edge region, it may be able to receive signalfrom multiple cell sites and the UE’s transmission may be received at multiple cell sites. Given that, if wecoordinate the signaling transmitted from the multiple cell sites, the DL performance can be increasesignificantly. This coordination can be simple as in the techniques that focus on interference avoidance ormore complex as in the case where the same data is transmitted from multiple cell sites. For the UL, since thesignal can be received by multiple cell sites, if the scheduling from the different cell sites, the system can takeadvantage of this multiple reception to significantly improve the link performance. In what follows, the COMParchitecture will first be discussed follow by the different schemes proposed for CoMP.5.5.2 COMP ARCHITECTURECoMP communications can occur with intra-site or inter-site CoMP as shown in Figure 18. With intra-siteCoMP, the coordination is within a cell site. The characteristics of each CoMP architecture are summarized inTable 3. An advantage of intra-site CoMP is that significant amount of exchange of information is possiblesince this communication within a site and does not involve the backhaul (connection between base stations).Inter-site CoMP involves the coordination of multiple sites for CoMP transmission. Consequently, theexchange of information will involve a backhaul. This type of CoMP may put additional burden andrequirement upon the backhaul design.34
Intra-site CoMPBS3BS2Inter-site CoMPCell0Cell1X2UE2BS4UE1BS0BS1Cell2BS5BS6Figure 18. An illustration of the inter-site and intra site CoMP.Table 3: Summary of the characteristics of each type of CoMP architectureIntra-eNBIntra-siteIntra-eNBInter-siteInter-eNBInter-site(1)Inter-eNBInter-site(2)Informationsharedbetween sitesVendorInternalInterfaceCSI/CQI,SchedulinginfoCSI/CQI,SchedulingInfoTraffic +CSI/CQI,SchedulingInfoCoMPAlgorithmsCoordinatedScheduling,CoordinatedBeamforming,JPCoordinatedScheduling,CoordinatedBeamforming,JPCoordinatedScheduling,CoordinatedBeamformingCoordinatedScheduling (CS),CoordinatedBeamforming,JPBackhaulPropertiesBaseband Interfaceover small distancesprovides very smalllatencies and amplebandwidthFiber-connectedRRH provides smalllatencies and amplebandwidthRequires smalllatencies only.Requires smalllatencies.Bandwidthdominated bytraffic.An interesting CoMP architecture is the one associated with a distributed eNB depicted in Figure 19. In thisparticular illustration, the radio remote units (RRU) of an eNB are located at different locations in space. Withthis architecture, although the CoMP coordination is within a single eNB, the CoMP transmission can behavelike inter-site CoMP instead.35
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 16 and 17: NOTE:Implementation complexity refe
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 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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