MIMO Introduction


    LTE is the abbreviation of Long Term Evolution, and its full name is 3GPP Long Term Evolution. In Chinese, it means 3GPP LTE Technology, the third generation partnership project(3GPP) standard, and the core technologies of 4G network are OFDM(Orthogonal Frequency Division Modulation) and MIMO(Multiple Input Multiple Output).

In today's world, the rapid development of personal communication greatly prompted the miniaturization and diversification of personal communications equipment. Besides, the ability of the data business, such as the multimedia message, online games, video on demand, music downloads, and the mobile TV business, greatly satisfied the needs of personal communication and entertainment. LTE is mainly for the high-speed data services. The data business mentioned above generally occurs in the indoor environment, which requires larger system capacity and better network quality. For operators, massive construction of indoor distribution system can effectively increases the absorptive capacity of indoor business and meet the needs of the high-end users in dense urban area as well.

At present, most indoor distribution systems are built in the times for 2G or 3G technology and it will be difficult and costly to transform the existing traditional systems into those for 4G technology. To solve this problem, the transformation plan of the distributed active antennas can be adopted. The plan is to transmit the lossless-combined signal of two lines LTE signals through the currently existing distribution system to the active module (before the distributed active antennas). The active module will split the combined signal into the original two lines of signal. Then the two lines of signal will be given out through the distributed active antennas----the dual polarization antennas. This plan can achieve the full characteristics of LTE MIMO technology without increasing a new channel for transmission, which greatly reduce the difficulty of construction and the extent of transformation.

According to the relevant research, 70% of the data service occurs in the indoor environment and the indoor data business occupies an important position in the mobile communication network. The construction of indoor coverage system is an important means to realize the in-depth coverage of LTE. And LTE MIMO is designed to realize the high-speed data throughput.

1) LTE SISO Solution
The two signal of the LTE signal source, one is accessed into the indoor distribution system, the other is accessed with the load.



2) LTE MIMO Solution
LTE take dual channels cover (support MIMO), the two signal of the LTE signal source accessed into the new built two way indoor distribution system separately.


3) LTE Active Antenna Solution
The two LTE signal supported by a set antenna system (single cable),its main principle is to deal with the frequency difference of the two LTE MIMO signal with the local module, transmit one of the signal into middle frequency and then combine with the other one, the combined signal transmit in the same antenna system, and reduction at the end port through the active antenna.



Comparison of LTE solution
1) Application for three LTE solutions



LTE MIMO Active Antenna

LTE SISO

LTE MIMO

Advantage

The various performances of frequency conversion system are quite the same with the passive dual-channel system, but there is significant improvement in cell capacity when compared with single-channel system, and the frequency conversion system can effectively ensure the advantages of performance of LTE system. In the frequency conversion system, there is no need to reconstruct the feeder lines and its difficulty of constructing implementation is low. Moreover, frequency conversion system, using the single-channel distribution system, can realize the flexible and convenient construction advantages of MIMO dual-channel transmission.

Only need to build a new indoor distribution system, less quantities,lower costs.

Supported the LTE MIMO, could improve the user peak rate / system capacity ( it works much better than Build a new way or renewal a way), and it does not affect the existing indoor distribution system at all.

Disadvantage

To increase the active antenna and active components, but no need to change the original indoor distribution system.

It could not play the LTE MIMO function well, and the user peak rate and system capacity are limited.

Need to build two new ways and should along the existing indoor distribution system, cost higher.

Application

Perfectly suitable for those main areas or buildings with high capacity requirements but not reconstructing the indoor distribution system. Having enormous advantages in the smooth evolution from 2G/3G to LTE.

It applies to that do not require too much business requirements, or could not build two new indoor distribution system due to the normal building are in implementation phase of property management or projects, or some key buildings are in non-key areas(eg, the five-star hotel's sun level, lift and so on).

It applies to the key buildings that requires a high capacity, need to build a new indoor distribution, or the key building could not renewal the existing system but need a high capacity.


2) Throughput Comparison

    Performance compare of three different LTE indoor coverage solutions: Suppose LTE SISO throughput =1


                    Solution of LTE indoor coverage

                    Throughput

                    LTE SISO

                    1

                    LTE MIMO

                    1.5-1.8

                    LTE Active Antenna

                    1.4-1.7



3) Coverage Cost Comparison
Cost compare of three different LTE indoor coverage solutions: Suppose LTE SISO cost =1(reuse)

                    Solution of LTE indoor coverage

                    Cost

                    LTE SISO

                    1

                    LTE MIMO

                    3

                    LTE Active Antenna

                    1.5


4) Coverage construction Comparison
The difficulty compare of three different LTE indoor coverage construction:

                    Solution of LTE indoor coverage

                    difficulty

                    LTE SISO

                    Very easy

                    LTE MIMO

                    Hard

                    LTE Active Antenna

                    easy


Working Diagram




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