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Robust Cascaded Ethernet-Based RRU for HA Application

IP.com Disclosure Number: IPCOM000241130D
Publication Date: 2015-Mar-30
Document File: 5 page(s) / 151K

Publishing Venue

The IP.com Prior Art Database

Abstract

Wireless networks cloud (WNC) is a novel wireless system architecture that utilizes the general IT-based platform to support all the baseband processing in radio access network, instead of the traditional DSP+FPGA model, to achieve high flexibility and efficiency. This novel architecture also induces new requirements for remote radio unit (RRU), such as synchronization, time division duplex (TDD) timing control, etc.. However, existing commodity RRU designed for the dedicated wireless standards, such as GSM, WiMAX, LTE, etc., is usually based on the CRPI or OBSAI interface to connect with BBU. It can not be connected to the general IT platform directly without interface modification. To solve these problems, the first TDD Ethernet based RRU prototype for the SDR BS is proposed in [1]. By providing the Ethernet interface, it can connect with the general IT platform seamlessly without any additional hardware at BBU side. However, with the emergence of the new 3GPP/IEEE standards, the adopted bandwidth become more and more wide, which can reach to 20MHz (LTE), and even 100MHz (LTE-A, using carrier aggregation). Besides, the multi-antenna technology is also widely utilized to improve the reliability and throughput. Therefore, I/Q data rate between the RRU and BBU is increased greatly. On the other hand, the RRU also needs to support the function of cascade, and the data rate will also be increased largely. In this scenario, only one physical fiber link can not satisfy the requirement.In our invention, in order to overcome the bottleneck of the data rate in cascaded RRU systems, a novel architecture that uses more than one fiber connection is introduced and the corresponding work flow is also provided, and the robust of the system is also improved.

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Robust Cascaded Ethernet

Robust Cascaded Ethernet- --Based RRU for HA Application Based RRU for HA Application

Figure below is the architecture of the cascaded RRU systems. In order to explain more clearly, we only consider the case of two Ethernet links.

BBU

RRU 1#

RRU 2#

RRU N#

0

M0

S0

M0

S0

M0

S0

LAN0

Local Data

Local Data

Local Data

1

M1

S1

M1

S1

M1

S1

Ethernet interface LAN1

Each RRU has four independent Ethernet interfaces. Two of them are the master Ethernet interfaces, and the other two are the slave Ethernet interfaces. The master interface can have the unique MAC address, and also has the IP address. However, the slave interface has no MAC address and IP address, and it only has the ability of transfer the Ethernet data packet.

In this architecture, there are two independent LANs, and these two LANs can not exchange the data packet without the help of the BBU. For example, if the Ethernet is transmitted from the Eth0 of the BBU, this packet will always be forwarded in LAN0. The local data in each RRU can use the any of the two Ethernet links to exchange its own data packet, which is determined in the DHCP discovery stage.

Work flow:

1. In the start up stage, the DHCP mechanism is used to allocate the IP for each RRU. When the RRU initialization is finished, it will transmit the DHCP request packet in these two Ethernet interface one by one until it receives the response packet in one of the interface, and the following data packet exchanging between the this RRU and the BBU will always based on this active Ethernet interface. Therefore, BBU can determine which Ethernet link to use depending on the throughput allocation and control.

1


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2. After the RRU obtain its IP address related information, it will act as the TCP server and listen on a dedicated port for BBU's connection. Each RRU can only support one TCP connection. BBU will act as the client in this TCP connection.

3. After the TCP connection is successfully setup, BBU will configure the BBU, including the network configuration and the wireless configuration.


4. The RRU will be started in normal working mode.

Robust Design

There are two technologies to guarantee the robust of this cascaded RRU system. One is the optical...