RNC in Pool to Enhance Network Reliability

7/29/2019 RNC in Pool to Enhance Network Reliability

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1 HUAWEI TECHNOLOGIES CO., LTD.

RNC in Pool to Enhance Network Reliability

Author: Hu Guang

[email protected]

Introduction

1.1 Mobile Broadband TrendSmartphones are undergoing rapid development. For example, the smartphone penetration is expected to be over50% by 2015 in Western European countries. This has been pushing data traffic into drastic increases.

Furthermore, this strong momentum is still gathering.

Smartphone penetration in Western European countries

Signaling flows are on fold increases as high-speed data services and smartphone applications are multiplying,

generating signaling storms. The signaling connections per hour on a typical smartphone are above five times overa feature phone. This is stimulating challenging demands on processing capacity of mobile network infrastructure.

In parallel, data services are contributing more profits than voice services, which once presented more profits to

operators. Therefore, surging data flows are another challenge following the signaling storms.


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Service trend on smart mobile terminals

1.2 Challenge of Mobile Broadband to Radio Network ControllerWith continuous development of smartphone and mobile internet, higher demands of signaling and larger data

traffic capacity are required to the mobile network. This sets higher demands on radio network controller (RNC)

in terms of both user-plane and control-plane capacity and reliability. Traditionally, if one RNC goes faulty, all theservices are interrupted on the NodeBs under this RNC. This is calling for new solution to ensure higher RNC

reliability.


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Solution

1.3 OverviewWith the RNC in Pool solution, an RNC is additionally configured with an interface Iur-p through which several

RNCs are connected to form a resource pool. The RNCs in the pool work in redundancy mode.

RNC in Pool networking

On an RNC in Pool network, two or more RNCs are connected to each other through the Iur-p interface. When

one RNC goes faulty, another RNC obtains the fault information through the Iur-p interface and takes over the

services that are provided by the faulty RNC.

1.4RNC in Pool High Reliability

The RNC in Pool high reliability is achieved by connecting a NodeB to two or more RNCs through the Iub

interface. The RNC that has the control right over dual-homing NodeBs is a primary RNC. When the primaryRNC goes faulty, the RNC control right change is triggered to enable other RNCs, to which the NodeB belongs, to

have the control right to restore services. This helps prevent service interruption on the network when one RNC isfaulty.


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RNC redundancy on an RNC in Pool network

Advantages: The RNC ID remains the same after the RNC control right changes, freeing of

configuration changes on other NEs.

With N+1 redundancy, one RNC can work as backup for several active RNCs. Thisraises hardware utilization and lowers hardware bills.

The RNCs in redundancy mode can still connect to NodeBs and provide services. Impact:

Dual-homing links must be configured on the Iub interface. Backup routes must be configured on the Iu interface. Backup hardware is required.

1.4.1 RNC Control Right Change ModesThe RNC control right change can be triggered manually or automatically.

Manually triggered RNC control right change

Having observed an alarm and exception and found that the RNC is faulty and an RNC

control right change is needed based on the fault type and severity, a duty staff in theequipment room manually triggers an RNC control right change so that one secondaryRNC takes over the control right over dual-homing NodeBs. After the RNC fault is

rectified, the duty staff can manually trigger an RNC control right change again to enable

the primary RNC to take back the control right over the dual-homing NodeBs.


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Manually triggered RNC control right change in an RNC in Pool network

Manually triggering is performed by the duty staff and is easily implemented. Therefore,

it is helpful in the initial stage of operating an RNC in Pool network.

Advantages: Manual triggering helps prevent possible impact brought by automatic triggering. For

example, online UEs are forcibly disconnected and single-homing NodeBs are out of

service after the RNC control right changes.

When the automatic redundancy function is enabled, manual triggering helps preventpossible impact brought by automatic triggering during such operations, such astransmission adjustment, device reset, and software upgrade.

Automatically triggered RNC control right change

On an RNC in Pool network, the RNCs with the same NodeB multi-homing relationship

periodically transmits heartbeat messages to each other over the Iur-p interface or overother standard interfaces when the Iur-p interface is faulty.

In this way, the RNCs detect the running status of each other. If no heartbeat message or

abnormal heartbeat message is detected, one secondary RNC automatically triggers anRNC control right change to take over the logical RNC to serve the dual-homingNodeBs. When the fault is rectified on the primary RNC, the secondary RNCs detect the

heartbeat message. Then, the secondary RNC decides to trigger an RNC control right toenable the primary RNC to take back the control right.


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Automatically triggered RNC control right change in an RNC in Pool network

Advantages: An RNC control right is automatically triggered. Therefore, interrupted services can

return normal in case of RNC faults caused by a natural disaster.

Impact: An automatic RNC control right change caused by any inaccurate detection brings

about adverse impact on network performance.

An unexpected RNC control right change may also be automatically triggered duringsome maintenance operations when the automatic redundancy function is enabled.


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ConclusionThe RNC in Pool solution aims to improve the RNC reliability by load sharing and RNC redundancy to sustainthe drastic development of mobile broadband, while increasing the capacity of a single RNC.

The RNC in Pool solution provides advantages as follows:

Each single RNC provides higher capacity, helping reducing the number of requiredRNCs.

The solution supports multiple logical RNCs and N+1 redundancy, helping increasehardware utilization.

The solution supports evolution to cloud-based network in terms of both hardware andsoftware architectures.

RNC in Pool to Enhance Network Reliability

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