Network Collaboration of TD-LTE

Network Collaboration of TD-LTE

Is there mutual interference between the TD-LTE and the current 2G system in the adjacent frequency? How can this problem be solved?

A: In actual network deployment, the F-band (1880-1915 MHz) TD-LTE base station will be affected by the stray/blocking/Intermodulation Interference of DCS1800, the Second Harmonic Interference of GSM900 and the interference of PHS Base Station.

Figure 1 frequency distribution chart near F band

The interference introduced by the 2G system is as follows:

Figure 2 F-band interference type

If GSM1800 uses high-end frequency (1865-1880 MHz) and F-Band Current Network TD-SCDMA/TD-LTE equipment anti-blocking ability is insufficient, will introduce blocking interference; due to the current network GSM 1800 base station in F band stray indicators are poor, it will produce stray interference to F band TD-LTE; If DCS1800 use high-end frequency (1850-1880 MHz) in addition, if the Intermodulation indicators of some GSM s1800 antenna feeds (including antennas, feeder and passive devices) are not up to standard (the current network outfield test is less than-133dBc), the risk of third-order Intermodulation Interference will occur; due to the substandard mutual adjustment indicators of some GSM antenna feeds (including antennas, feeder and passive devices), the risk of Second Harmonic Interference of GSM will be generated;

For different types of interference, you can use the solutions listed in the following table.

Is there mutual interference between the TD-LTE and the current 3G system in the adjacent frequency? How can this problem be solved?

A: When the adjacent TD-LTE and TD-SCDMA systems coexist with cross time slots, there will be interference between the base station; when the two systems upstream and downstream time slot synchronization, there will be interference between the base station and the terminal. When cross time slots exist in the adjacent frequency TD-LTE and TD-SCDMA system, according to the calculation of the deterministic method, in the worst case (the direction of the antenna Main valve is positive ), the two system base stations must be separated by a space of at least 70 kilometers to coexist. Therefore, under normal network deployment, there must be severe interference between the two system base stations working on cross time slots.

In order to solve the cross time slot interference, the upper and lower time slot synchronization must be ensured between the TD-LTE and the TD-SCDMA system working in the adjacent frequency of F band. At this time, the interference between the base stations of the two systems is completely avoided, and there will be some interference between the base station and the terminal. However, according to the study of the coexistence in 3GPP, as long as the base stations and terminals of the two systems meet the RF indicators (mainly ACLR and ACS) in the current 3GPP standard, interference between the base stations and terminals can be ignored.

For example, when the TD-LTE selects the sub-frame ratio 2, the special sub-frame ratio 5 (that is,), the frame sequence relationship between the TD-SCDMA and the TD-LTE dual-mode network is shown in:

It can be seen that when the TD-S system works in the upper line, the TD-L system is either in the protective time slot (neither launch nor receive), or in the uplink time slot. Therefore, when the parameters of the base station are reasonably configured, the two systems will not interfere with each other if the upper and lower time slots are not staggered.

Is there mutual interference between the TD-LTE and the current WLAN system when the adjacent frequency coexist? How can this problem be solved?

A: The TD-LTE indoor base station or room system uses E band (2320MHz ~ 2370 MHz), and 2.4 GHz WLAN (MHz ~ 2495 MHz. Due to the good anti-interference performance of LTE base stations and terminals, WLAN has relatively little interference with LTE, while LTE base stations have serious interference with wlan ap and LTE terminals.

For scenarios where an LTE base station interferes with a wlan ap, the wlan ap is deployed and close to the LTE antenna point, inter-office construction can be deployed to avoid interference between the LTE base station and AP. For example, when the WLAN system must be deployed with a mounted AP, the physical distance between the WLAN and the LTE antenna point must be around 4 meters.

The interference of LTE terminals to WLAN terminals mainly occurs in scenarios with weak LTE coverage. At this time, the launch power of LTE terminals is high. If the terminal distance is close, it may cause great interference to WLAN terminals. This scenario can reduce interference to WLAN terminals by increasing the terminal spacing or increasing the coverage level of the LTE system (reducing the terminal transmit power. Interference between the LTE and WLAN modules in the terminal can also be solved through coordination between modules, such as time division or frequency division multiplexing.