Auto-Configuration of Wireless Cell-Site Surnjani Djoko, Hee Lee, Kalyan Basu Nortel Networks, Global Wireless Internet Engineering 2201 Lakeside Blvd Richardson, TX 75083
[email protected] Abstract- In a telecommunication network, when a new network element is installed into the network, the new network element has to take the responsibility to fit itself into the network by forcing the changes in the existing network elements through the configuration processes. This paper describes an approach that allows the new network element being accepted by the existing network through auto configuration and topology management functions. This makes the configuration management process of the telecommunication network simple, less expensive & less error prone.
1. INTRODUCTION The configuration management is responsible for putting the network in place. One of the tasks of configuration management is resource provisioning, which ensures procurement, deployment, and configuration of the necessary resources (both hardware and software) in time to meet anticipated customer demand for an economic engineering interval. The resource provisioning functions could be range from network capacity monitoring, hardware installing, software loading, translations loading, configuration testing, resource databases updating, to introducing a new configuration of the network for services. The software loading is the process of entering software into network elements like the old system of booting a cold system. The loading process can occur in the initial installation of hardware or hardware extension. It may also occur at the periodic software feature upgrade. The translation loading is the process of filling in the data-fill of resource configurations and service profiles. Collectively, configuration management processes represent more than 50% of typical network operating expense. The rapid growth and change in services and technologies, is increasing the frequencies of activation of configuration management process. At the same time, the complexity of the network and services are increasing due to the addition of new network elements for data and multi media services. This is causing the need to rapid evolution of the configuration processes. The thrust on e-business in the carriers creates the opportunity to have a new look to the configuration management process, and utilize the new hardware and software technologies integrated with IP network to reduce cost. The scope of this paper is to cover the activation of a cellsite after hardware installation and network connection. This includes loading the appropriate software loads in the cell-site and the radios, establishing the different translations and data structure to meet the configuration needs of the cell-site with
respect to the network topology and the setting the different software parameters for hardware and software provisioning. In the next sections, we describe the current configuration process, and will introduce the concept of ‘auto configuration for wireless cell-site’. The concept is explained using a new network element of a cell site connected to a private IP network architecture. It should be easily applicable to other network elements like BSC (Base Station Controller), SGSN (Serving GPRS Switching Node), GGSN (Gateway GPRS Serving Node), GW (Gateway), and Call server. The effort has been made to integrate a specialized configuration server in the solution to increase customer value.
2. CURRENT CONFIGURATION MANAGEMENT PROCESS Telecommunications networks continue to grow at an exponential rate. The growth has led to the installation of many network elements. The legacy wireless network of GSM, TDMA and CDMA access technologies, use the old styled OAM&P (Operation, Administration, Management and Provisioning) structure that is too slow to respond or too labor intensive. The complex resource provisioning of wireless requires many activities. To add a new customer in the network will need many parameters activation. This results in delay in adding new customer in the network, as well as last minute changes that increases the operating company expenses. Software upgrading, which is quite frequent, typically requires several hours for a system. Service and resource translations must often be extracted from working systems manually, data is updated and repackaged and finally reentered. Re-keying of data is also prone to error. As more of the network becomes software driven, programs and data-fill more voluminous, effective ways to cut these unloadlreload intervals and reduce configuration data-fill errors must be devised. Today each network element has its specific processes for physical installation, network connectivity, and configuration (loading of software image and optimization of parameters). The costs associated with installation of the equipment and establishment of physical connection to the network are almost fixed. However, the steps following installation are mostly not a fixed cost, and they can be under the control of the OAM&P functionality. IP networks in contrast to legacy telecommunications systems have utilized mechanisms that are simple and hence cost effective [l]. In the complex network environment, IP networks allow the new network element being accepted by the existing network through auto configuration and topology management functions. In contrast, in telecommunication
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network, the new network element has to take the responsibility to fit itself into the network by forcing the changes in the existing network elements through the configuration processes. This makes the configuration management process of the telecommunication network very complex and expensive. It is time to analyze such mechanisms that have eluded our attention due to many regulatory reasons and lack of knowledge on the simplicity of IP networking concepts. Hence by extending and adopting such non-complex means, it is our hope that cost structures could be altered to enhance competitiveness.
3.
AUTO-CONFIGURATION MANAGEMENT
A network architecture shown in Figure 1 consists of a cell site connected to the private IP network through a router. In the private network, there are databases to store network information and configuration information to be accessed by OAM server through LDAP, a load" server for storing software loading, DHCP servers for giving out the basic IP parameters, and a cell site OAM server for managing the cell sites. Each cell site has a number of radios (depends on the number of sectors in the cell site), and each radio has its own agent.
3.1
Fig. 1. Network OA&M architecture
3.I . 1
Network managedoAM server
Network manager is responsible to configure the cell-sites along with all radios and ensure the correctness and integrity of the topology of the network. It communicates with the different agents of the cell-site through SNMP. The agents send traps to the network manager to signal the status and to indicate what is wrong with the different sub systems of the cell-sites and radios. The manager will communicate back with the different agents through SNMP. In addition, the OAM server will access the configuration parameters in the databases through LDAP protocol. The server also access the specialized configuration server to use the special functions like AFP (Advanced Frequency Planning), Software parameter optimization algorithm etc to insert the specialized parameters of the load for the cell.
3.1.2
DHCP server
MIBs inside the radio to store the configuration parameters
The Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configurations information (basic IP parameters) to hosts on a TCPAP network. DHCP uses UDP as its transport protocol. DHCP messages from a client (cell- site agents) to a DHCP server are sent to the 'DHCP server' port 67, and DHCP messages from a server to a client are sent to the 'DHCP client' port 68. For the cell-site configuration, DHCP is used as automatic allocation to assign basic IP parameters (radio's IP address & subnet, TFTP server IP address for downloading software, software load name, network manager IP address) to the different agents of the cell-site.
Network manager (OAM server)
3.1.3
Auto-configuration requirements
To configure a network element (i.e., radio), the followings are needed: SNMP agent reside in a radio
Database server Specialized configuration Server Communication protocol between agent and network manager (SNMP) Communication protocol between manager and database server (LDAP)
network
The TFTP server is a server, which contains the software load. The load default directory is in Itftpboot. To prepare the load, the OAM server will use the service of the specialized configuration server and use that functionality to configure the load with correct set of parameters. The load directory should be given under the default directory. 3.1.4
Communication protocol to obtain basic IP parameters from DHCP server (DHCP) Communication protocol to obtain software load from load server (TFTP)
TFTP server
Database
The database consists of the cell-site and radio parameters. It can be modeled using UML, and be accessed by the network manager through LDAP. The model consists of data model as well as relationship model. The data model is a collection of classes and attributes that represent the data characteristics of the system being modeled. The relationship model describes how different objects are related to one another.
3.1.5
Specialized configuration server
Since it is not possible for the network manager to automate and correctly configure all aspects of the radios and cell-sites, the specialized configuration server has the capability of providing a foundation for rules information to guide how the parameters can be configured correctly. The rules are extracted from the domain experts and stored inside the server, and the server will get input from several tools
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such as Planet outputs of FZF design, self-engineering algorithm [5] for handoff parameters optimization, AFP [4], etc. When a configuration is added to the database from those tools, its rules information is checked to determine if the configuration is correctly filled. Hence, The specialized configuration server is very valuable component to reduce most of the manual works of engineering and provisioning and interlinking with the load creation.
3.2
updates related tables. OAM server informs the other network elements such as BSC's, MSC's, GGSN's manager, the present of the cell site in the network o OAM server receives confirmation from the BSC, MSC, SGSN, GGSN managers that the cell-site has been accepted as a valid network element in the network and their respective system and topology parameters are updated for this cell-site After the completion of all updates, the OAM server to further verify the radio's ability to handle calls by running a testing called "test call". The radio goes to inservice and unlocked state once the test is passed
Auto-configuration process
Before the configuration process is performed, the hardware installation has to take place first, followed by the parameters configuration [2], [3] and databases update. The steps are as follows: Hardware installation begins by a cell-site is plugged into a network; it is in un-configured and locked state. The cell-site and radios will perform power up, install base software followed by hard reset and self testing Cell-site and Radio configuration: o Initially, when a cell-site has been installed into the network, the radio agents will broadcast a DHCP message to all DHCP servers in the subnet. The messages to obtain basic IP parameters o Once the basic parameters are obtained, the agent will check the flash memory for the loadname. If the load-name is present and the name is the same as given by the DHCP response, the respective subsystems and radios will boot the load from the flash. Otherwise, the subsystem agents and radio agents will open a TFTP session to load server given by the DHCP response, and transfer the load file to RAM. Then make sure the load is valid free of error (otherwise, reset and retry to load until the load is valid) o After the load is obtained, the subsystems and radios will reset, boot the load from the flash, and performs soft reset o The subsystems and radio agents will request the remaining of the parameters for configuration from the OAM server identified by DHCP response o After the configuration is completed, the subsystems and radio agents are in the configured and locked state o The OAM server initiates the subsystems and radios to return to service state through SNMP message to their respective agents o The subsystems and radios run the diagnostics test, and inform the OAM server the results of the test through SNMP message Databases update: o If the test is passed, the OAM server will add the cell site with its radios to its databases and
3.3
Radio parameters
Radio's parameters exist at several levels, factory programmed configuration (unit identifier, hardware versionhelease number, date manufactured, and Ethernet MAC address) and non-factory parameter configuration (physical interconnection, resource assignment, application, and call processing). The non-factory parameter configuration is loaded into the radio through SNMP. The following parameters have been identified (not a complete list) as needed to be data-filled within the radio prior to operation: o
Basic IP parameters (from DHCP server): assigned IP address, TFTP server IP address, relay agent IP address, subnet mask, software load-name, and OA&M server IP address o The rests of the parameters should be obtained from OA&M server through SNMP: o Power control configuration (enabling conditions, power control algorithm selection, maximum authorized power, signal reception level and quality, starting conditions, and mobile transmission power steps). The specialized configuration server helps the OAM server to compute the correct setting of these parameters o Adjacent cell configuration (indicates the neighbor cells of the serving cells for handoverlhandoff). The specialized configuration server provides the parameters o Handoff configuration (enabling conditions, level and quality of thresholds, average distance computing parameters, level, quality, interference, and corrective factors used for missing measurements). The specialized configuration server provides the parameters o All different types of control and voice/traffic channel configuration. The specialized configuration server provides the parameters Each of the parameter is a MIB element.
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4. CONCLUSION This paper describes an approach that allows a new network element being accepted by the existing network through auto configuration and topology management functions. Furthermore, it introduces configuration server in the solution that get input from several tools to make sure the configuration information is added correctly into the databases. This makes the configuration management process of the telecommunication network simple, less expensive and error prone. The paper presents an example of autoconfiguration for a wireless cell-site. The approach should be easily applicable to other network elements like BSC, SGSN, GGSN, RAN, GW, and Call server.
REFERENCES [ 11 Sidarth Ambardar, Walter Lazear, “Dynamic Router
[2] [3] [4] [5]
Configuration Management for Wireless Mobile Environments”, RAWCON’98. “OA&M System Description for the Edge Composite Data Network”, release 0.1, Nortel Networks. “GPRS-136HS (EDGE) Cell Site High Level Design”, Nortel Networks Chang Yu, “Advanced Frequency Planning”, Nortel Networks. Hee Lee, Surnjani Djoko, Hua Jiang, “Wireless Network Self Engineering Engine”, Network’98.
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