PDP Address Allocation | LTE AND IPV6

PDP addresses are handled differently for PDN interworking of type PPP and IP (IPv4 or IPv6).

Interworking with PDN Based on IP

During PDP context activation, the MS can configure an IPv4 address, or obtain an IPv6 interface identifier to be used during the IETF-based IP address allocation after PDP context establishment.
The MS can obtain an IPv4 address or an IPv6 prefix via an IETF-based IP address allocation mechanism once the PDP context is established.
The EPS specifies the following IETF-based IP address/prefix allocation methods:
  1. IPv4 parameter configuration and IPv4 address allocation through the DHCPv4.
  2. IPv6 parameter configuration through a stateless DHCPv6
  3. /64 IPv6 prefix allocation through IPv6 stateless address autoconfiguration
The MS releases any allocated IPv4 address or IPv6 prefix locally for the corresponding PDN connection upon deactivation of a default PDP context.

Interworking with PDN Based on PPP

No PDP address is configured during PDP context activation. Instead, such information is negotiated and configured during the NCP phase of PPP.

IP Address Allocation via NAS Signalling

The MS sets the PDP type in the PDP address field using the ACTIVATE PDP CONTEXT REQUEST message. This is done when requesting default PDP context establishment.
If the MS requires using DHCPv4 for IPv4 address assignment, it indicates that to the network within the Protocol Configuration Options in the ACTIVATE PDP CONTEXT REQUEST message.
When the MS requests IPv6 address allocation, the network accommodates it in one of two parts: a /64 IPv6 prefix and an interface identifier of 64 bits length. The MSN doesn't use the IPv6 prefix part immediately by the MS; however, the network uses the same IPv6 prefix in IETF-based IP address allocation subsequent procedures. The interface identifier is only used to build a unique link-local IPv6 address.

IPv6 Networks and LTE

In EPC architecture there are two gateways that may be combined into a single network element; the SGW and the PGW (Figure 1). If these two gateways are separate network elements, there are two options for the protocol being used among them: GPRS Tunneling Protocol (GTP) and Proxy Mobile IP v6 (PMIPv6) .

Figure 1: All-IP LTE structure
The Release 8 specification identifies EPS bearers similar to the concept of PDP Context, which is defined in 3GPP's Release 7 specifications. An EPS bearer is a logical connection between a UE and a gateway, associated with a specific QoS class. As long as these Service Data Flows (SDFs) belong to the same QoS class, an EPS bearer can carry multiple SDFs.
An EPS bearer can carry both native IPv6 and IPv4 traffic in contrast to the PDP Context defined in 3 GPP Release 7. Therefore IPv4 and IPv6 stacks can be supported by a UE simultaneously as long as it's connected via a single EPS bearer.
Regarding the IPv4 scarce address resources, allocating both IPv6 and IPv4 addresses to a device does not solve the problem of IPv4 exhaustion. A service provider may therefore decide to assign only IPv6 addresses to certain devices, even when the device is able to support IPv4 and IPv6 simultaneously. In that case, NAT-PT or IPv6-toIPv4 http-proxy functionality may be required to connect these IPv6-only devices with legacy IPv4 end-points. Such a decision needs careful consideration and the issues identified in RFC 4966 need to be taken into account.
A User Equipment device (UE) obtains an IP address in one of the following two methods:
  1. As part of the attachment procedure
  2. Via a separate assignment procedure, such as DHCP or IPv6 Stateless Address Autoconfiguration.
The attachment procedure consists of the following steps:
  1. The UE requests an attachment via sending a message to the MME, followed by an authentication procedure involving the HS S. The HSS sends to the MME, subscription data associated with the user as part of this procedure.
  2. With a few exceptions, the MME is responsible for selecting the Serving and PDN Gateways that will be used for this UE. It sends a request for the establishment of the default bearer to the SGW, which forwards it to the PGW. This message exchanges results in the establishment of a GTP tunnel or a Mobile IP tunnel segment between SGW and PGW. As long as the user is attached, this segment remains up, even when the UE enters the idle state.
  3. The MME orchestrates the establishment of the GTP tunnel segment between SGW and eNB and the (default) radio bearer between eNB and UE. The bearer between SGW and UE is torn down whenever the UE goes to idle state. If the SGW receives IP packets destined for the UE while it is in idle state, the SGW triggers the MME which starts a paging procedure.
When the IP address assignment is part of the attachment procedure, an IP address is allocated by the PGW to the UE according to step 2. This IP address is provided to the UE within the GTP control messages being used for establishing the EPS bearer according to step 3.
When a default bearer is established (disregarding the IP address assignment), DHCP or IPv6 Stateless Address Autoconfiguration (SLAAC) can be performed by the UE for obtaining an IP address. Therefore, a UE could receive an IPv4 address during the attachment procedure and an additional IPv6 address through SLAAC procedure.

PDP Context | LTE AND IPV6

A PDP context is a data protocol structure that is present on both SGSN and GGSN. It contains information regarding the subscriber's session during subscriber's active session. The subscriber-related data within the PDP context information includes: IP address, IMSI information, and Tunnel ID (TEID). Therefore access to the external packet-switching network can be achieved through a PDP context specification. The data associated to the PDP context is consisted of information including the MS PDP address (IP address), the packet-switching network type, the GGSN reference, and the requested QoS. A PDP context is identified and handled by a mobile's PDP address within the following entities: SGSN and GGSN and the MS. Within a given MS several PDP contexts can be activated at the same time.

APDP context is created through a PDP context activation procedure, which may be initiated either by the network or by the MS. Before PDP context negotiation, the MS is always GPRS-attached.
To remove a PDP context a PDP context deactivation procedure is required. This procedure may be initiated either by the network (SGSN or GGSN) or through the MS itself. The PDP context deactivation procedure may be initiated either during the GPRS detach, delete subscriber data procedures, or during an application deactivation.

EPC Challenges | LTE AND IPV6

The EPC changes key networking paradigms for previous mobile generations (2G/3G) core networks and the integration of EPC is expected to address a number of technological challenges successfully.

The radio side in LTE (eNodeB) has undergone significant technological advances to provide wider spectral bands and efficient use of the spectrum, which are reserved for LTE, which results greater performance and system capacity. At the same pace, the mobile core is required to change and to provide higher throughput while maintaining low latency; both due to the improved and simplified flat all-IP network architecture.
The important aspect of LTE is the introduction of new technologies and the delivery of the high performance LTE solution, which are both involved on the radio side.
The EPC needs to address the following key aspects of IP for the LTE deployment:
  1. Distributed versus centralized network architectures, including; SGW, PGW, and MME deployment.
  2. Network addressing and IP routing, and realtime management for large IP domains.
  3. The introduction, strategy, and coordination of IPv6 and its interoperability with IPv4.
  4. End-to-end deployment for QoS and underlying transport coordination.
  5. Data and control plane end-to-end security.
  6. Layer 2 versus Layer 3 transport layer connectivity (eNodeB, PGW, SGW, MME).
  7. External networks and VPNs interconnectivity.
  8. Lawful Interception and Deep Packet Inspection (DPI).
There is a set of stringent requirements for scalability, reliability, and high-performance elements because of LTE's dynamic nature of user mobility, which are coupled with the large-scale deployment targets and short duration of multiple data sessions for each UE.
To satisfy these requirements, the EPC elements must have the best classification with high IP performance. In order to address all these fundamental aspects of EPC's and according to the network element and product level, a new generation of scalable mobile core equipment, purpose-built, and strong IP expertise are required.
It is important to integrate all these elements together to deliver the needed carrier-grade features for LTE. The EPC elements must fully interwork harmoniously while in both control and user planes, the fairly complex network procedures involve all EPC elements. The EPC is expected to address the demanding requirements for dynamic and multi-dimensional mobility management, policies and data bearers. This should be done in an orchestrated manner to enable the highest LTE performance, while offering interoperability and interworking with the legacy 3G/2G systems.

Introduction to Evolved Packet Core (EPC) | LTE AND IPV6

Apart of LTE contains EPC, which is a new system design based on the all-IP mobile core network architecture. EPC forms a converged framework based on real-time and non-real-time packet-based services. EPC is specified by 3GPP Release 8 standards.

The EPC is responsible for providing mobile core functionality, which used to be two separate sub-domains in previous mobile generations (2G, 3G). These two sub-domains are: Circuit-Switched (CS) (i.e., supporting voice) and Packet-Switched (PS) (i.e., supporting data). These two distinct sub-domains are used for individual mobile voice and data switching and processing under a unified single IP mobile domain. LTE offers an end-to-end IP-based architecture, which covers from the mobile handsets and other terminal devices offering embedded IP capabilities on top of LTE base stations. The LTE base station is an IP-based device often called Evolved NodeB.
LTE's EPC is an essential functional entity offering end-to-end IP service, as well as allowing the introduction and creation of new business models, including partnerships and revenue sharing with application and third-party content providers. EPC promotes the enablement of new applications and new innovative services.
EPC addresses those fundamental requirements of LTE that deal with media-rich and advanced real-time services offering enhanced Quality of Experience (QoE). Network performance can be improved using EPC. This is done by separating data and control planes by using a flat IP architecture that is able to reduce the hierarchy delay among mobile data elements. For instance, the data path traversing from eNodeB passes only through EPC gateways.
The introduction of the all-IP network architectural EPC in the design of mobile networks has caused various degrees of implications on the following mechanisms:
  • All-IP mobile services, such as; IP-based voice, data and video communications.
  • New mobile architecture interworking with previous mobile generations (2G/3G)
  • Network scalability, which is required by all core elements to address any changes in the bandwidth and the number of user-terminal direct connections.
  • Availability and reliability offered by each elements ensuring service continuity.
To address various service and network requirements, the EPC is designed in such a way to change the existing mobile network paradigms.
The following subcomponents are part of the EPC architecture:
  • MME (Mobility Management Entity): In LTE, the MME is a key control-node for the access network method. MME is responsible for paging procedure including retransmissions and the UE (User Equipment) tracking idle mode. It is also responsible for match an appropriate SGW for a UE at the time of intra-LTE handover that involves the Core Network (CN) node relocation and at the initial attach time. MME is further involved in the user (by interacting with the HSS) authentication and the bearer activation/deactivation procedures. The MME can terminate the non-Access Stratum (NAS) signaling can generate and allocate temporary identities for UEs. It also checks for the authorization of the UE for camping on the service provider's Public Land Mobile Network (PLMN) and enforcing UE roaming restrictions. The MME handles the security key management and is the termination point in the network for ciphering/integrity protection for NAS signaling. The MME also offers lawful signaling and LTE/2G/3G mobility control plane functions with the S3 interface that terminates at the MME from SGSN. The S6a interface is also terminated by MME towards the home HSS for UEs roaming purposes. The following interfaces were considered for MME:
    • S3: This interface enables bearer and user exchange information for inter 3GPP access network mobility between SGSNs.
    • S6a: This interface enables subscription and authentication data transfer for authenticating and authorizing user access.
  • PGW (PDN Gateway): From the UE to the external packet data networks, PDN Gateway provides connectivity by providing the point of entry and exit for the UE's traffic. More than one PGWs may provide simultaneous connectivity for a UE providing multiple PDN access. The PGW performs packet filtering for each user, policy enforcement, lawful Interception, charging support, and packet screening. The PGW may act as the anchor for mobility between non-3GPP and 3GPP technologies, which is nother key role of PGW. These technologies include: 3GPP2 (CDMA IX and EvDO), WiMAX and etc.
  • SGW (Serving Gateway): User data packets are routed and forwarded by the SGW. During inter-eNodeB handovers the SGW acts as a mobility anchor for the user plane. It also acts as an anchor for mobility among LTE and other 3GPP technologies, where it can terminate the S4 interface and relay the traffic among PGW and 2G/3G systems. The SGW terminates the DL data path for the idle state of UEs and when DL data arrives for the UE, it triggers paging. The SGW also stores and manages UE contexts, such as parameters of network internal routing information and the IP bearer service. In case of lawful interception, it also performs replication of the user traffic.
  • PCRF (Policy and Charging Rules Function): Though PGW, SGW, and MME were introduced in 3GPP Release 8, PCRF was part of 3GPP Release 7 introduction. Architectures using PCRF have not so far been widely adopted by standards, however the interoperability of PCRF's with the EPC gateways and the MME is essential for the operation of the LTE and mandated in Release 8.

The IPv6 Transition Mechanisms | Long Term Evolution (LTE)

IPv6 was designed with a long transition period in mind. Therefore there is a myriad of IPv4 to IPv6 transition mechanisms have been defined in the various RFCs. The transition mechanisms can be grouped into a few categories (3G Americas, 2008):
  1. Dual Stack
  2. IPv6 tunneling over IPv4
  3. IPv4 - IPv6 translation

1 Dual Stack

In a dual stack mechanism, the device supports both IPv6 and IPv4, which means that the device is able to obtain both IPv6 and IPv4 addresses from the network and is able to choose either IP version to use to communicate depending on the IP version and the peer supports. The IP version and the peer supports can be discovered, for example, using a DNS service. 

2 IPv6 Tunneling over IPv4

When two IPv6 domains are not directly connected over IPv6 but instead are connected through an IPv4 network, which is often the case during the initial transition of the Internet to IPv6, IPv6 traffic will be tunneled over IPv4. The following tunneling techniques that may be relevant to IPv6 migration are:
  • Configured tunnels: This is used for connecting two IPv6 domains that have native IPv6 connectivity. The tunnel (typically from router to router) is configured via administrative means. IPv6 packets are encapsulated in IPv4 packets.

  • Tunnel broker: Tunnel broker is a technique that uses an IPv6 domain (a network or an individual host), which establishes an IPv6 connectivity using such a tunnel broker, serving as a virtual IPv6 ISP.

  • 6to4: This is used for deploying IPv6 in a network without waiting for the administrator of the network to provide native IPv6 connectivity. A 6to4 router advertises a global unicast IPv6 prefix to the network, constructed from a public IPv4 address assigned to the network. The 6to4 router also acts as a tunnel endpoint for the network. IPv6 packets are encapsulated in IPv4 packets. The IPv6-in-IPv4 tunnels between 6to4 sites are established automatically. The 6to4 relay routers allow 6to4 sites to communicate with native IPv6 sites.

  • Teredo: Teredo is used for deploying IPv6 in a network without waiting for the administrator of the network to provide native IPv6 connectivity (similar to 6to4). This is particularly important when the network is behind a NAT and the NAT system is not upgradeable to provide 6to4 functionality, since the 6to4 router cannot sit behind an IPv4 NAT. In Teredo, a Teredo server deployed in front of the NAT, serves as the IPv6 router for the network, transmitting IPv6 router advertisements with a global unicast IPv6 prefix, constructed from a public IPv4 address assigned to the network. This helps the hosts behind the NAT (the Teredo clients) learn about their assigned public IP address and UDP port and enable hole punching through the NAT for Teredo clients between sites to establish direct connectivity. Teredo relays allow Teredo sites to communicate with native IPv6 sites.

  • ISATAP: The ISATAP is an IPv6-in-IPv4 tunneling technique that allows dual-stack hosts and routers within a network segment to communicate over IPv6 when the IP infrastructure within the network segment does not support native IPv6. One example scenario is to allow a host to access the Internet via IPv6 when a site has native IPv6 access to the Internet, however the host happens to be within a network segment that has not been upgraded to IPv6.

3 IPv4 - IPv6 Translation

When an IPv6-only host needs to communicate with an IPv4-only, some form of protocol translation is needed. The following translation techniques have been developed:
  • NAT-PT (Network Address Translation — Protocol Translation) and SIIT (Stateless IP/ICMP Translation Algorithm).

  • IPv6-to-IPv4 Transport Relay Translator: A TRT is a TCP or UDP relay which additionally performs IPv4 — IPv6 translation.

IPv6 versus IPv4

Internet Protocol version 6 (IPv6), also known as the Internet Protocol next generation (IPng) is intended to sustain constant Internet growth with consideration of the number of users and functionality. The legacy IP version, IPv4, was implemented in the early 1980's based on stationary wired communication infrastructure. The IPv4 supports less than 232 (over 4 billion) individual addresses, hence IPv4 suffers some limitations that may be inhibitors to growth of "tomorrow's" Internet, and use of the Internet as a global networking solution. Therefore, IPv6 is under development to take over IPv4's position by providing a greater expansion of IP address space; nonetheless, incorporating features of such include end-to-end security, mobile communications, Quality of Service (QoS), and system management burden reduction.

Without adequate global IP address space, applications have to work in such ways to afford local addressing. In a short-term, there have been various discretionary "workarounds" and extensions to IPv4 in and attempt to overcome its limitations. Network Address Translation (NAT) enables multiple devices to utilize local private addresses within an enterprise at the same time sharing one or more global IPv4 addresses for external communications. While NAT, to a certain degree, has postponed the exhaustion on IPv4 address space for the time being, it also complicates common application bi-directional communication. IPv6 simplifies the confusion of presenting an end-to-end security and eliminates the general incentive for using NAT since global addresses will be extensively accessible.

IPv4 had numerous issues, one of which was not having sufficient geographical distribution; it currently has less than 50% coverage throughout the USA. One the other hand, routing was too complex for new technologies and features such as mobile computing had coverage areas issues. Most significantly, the number of IP addresses is reaching its limit and the time has come to adopt IPv6 to compensate for the technical and address space requirements. Figure 1 shows IPv4 and IPv6 header formats.

Figure 1: IPv6 versus IPv4 header
Table 1 shows the differences in the IPv4 and IPv6 headers fields' differences. As shown, IPv6 offers a few additional fields compared to IPv4.

Table 1: IPv6/IPv4 header field differences 
IPv4 Header field
IPv6 Header field
Traffic class filed (QoS parameter)
Total length
Payload length
The Next header
Flow label (QoS parameter)
Next Header
The source address and destination addresses are based on 32-bits address fields
The source address and destination addresses are based on 128-bits address fields

INTRODUCTION TO IPV6 | Long Term Evolution (LTE)

IPv6 is, by far, one of the most important and significant technology and network upgrades in the communication history. This upgrade is growing slowly and will eventually terminate IPv4's network deployment at the end of the transition phase. IPv6 is designed to work with high speed network and low bandwidth networks, particularly suitable for wireless networks. The IPv6 design accommodates new technology requirements, such as QoS, security, and of course extended addressing.

Since the mid 90's many developers and researchers have been working on IPv6 and many RFCs are directly or indirectly discussing this technology. RFC 1883, released in 1995, is the first RFC in regards to IPv6. These efforts have been initiated and monitored by the Internet Engineering Task Force (IETF).

In the past several years IPv6 has deeply penetrated into the architecture of the Internet. Figure 1 (adapted from Gallaher & Rowe, 2005) presents a penetration estimates of IPv6 in the United States, which shows that by year 2010, almost 30% of ISPs and 18% of the users will be switching to IPv6.

Figure 1: IPv6 penetration in vendors, ISPs, and users
The main issue with IPv6 integration is its interoperability with IPv4. IPv4 is going to be around for at least a decade before all the networks are purely running over IPv6. Therefore it is essential to ensure IPv6 traffic flows are not going to have any negative impacts on IPv4 and vice versa. Dual-stack systems are considered a solution for the IPv6/IPv4 interoperability issue, which are going to be utilized in the design and implementation of systems for sustaining both IPv4 and IPv6 parallel processing to guarantee interoperability amongst the two protocol suites.

Mobility is another major features that is going to be impacted by this transition. 3G networks have been growing immensely in the past few years and IP connectivity has become an inseparable part of the 3G networks. The involvement of IP is going to increase more as 4G networks are becoming realizable. These requirements are being considered in the IPv6 applications.

This chapter will explore IPv6 features, in particular, in conjunction with LTE architecture. At first, IPv6 is going to be discussed and compared to IPv4. Following this introduction, IPv4-to-IPv6 transition, IPv6 security, Mobile-IPv6, and QoS-IPv6 are covered.

Automatic Router Configuration | Solutions and Recommendations

Automatic configuration of the WR is performed using a 4-state machine including a start up state, a learning state, an operational state and a site down state as depicted in Figure 1.

Figure 1: A state machine for dynamic configuration of a wireless router
The WR configures the RF/IP topology in the startup state, and refines the topology in the learning state. In the operational state, the wireless router handles a full traffic load, and continues to check if it meets the operational thresholds. Scheduled or unscheduled maintenance leads the WR into site-down state.

1) Start up state: In the starting state, connectivity is first established between the WR and the wire-line routers in the network. The wire-line connectivity is then used to establish connectivity between WR and its WR neighbors. Subsequently, MPLS paths or other suitable virtual circuits or IP tunnels are established among the WR neighbors to facilitate inter-router communication. The WR uses wire-line connectivity to learn from its neighbors the RF topology in the neighborhood, and establish wireless-specific connectivity with its neighbors.

After establishing the wireless connectivity with its WR neighbors, a WR exchanges RF impact information, including some or all of the parameters mentioned earlier. By exchanging this information, and negotiating the various operation parameters, the WR is able to determine or estimate a set of operating parameters that will help maximize radio coverage, minimize interference, and aid in providing a seamless coverage from cell to cell with smooth handovers. If no coordination could be achieved between the wireless routers in a neighborhood, Operation, Administration and Maintenance (OAM) server is contacted for resolving the differences. The OAM server then performs the RF impact analysis and responds with the operational parameters for the new site and the neighboring sites. The OAM server may also re-identify neighbor sites after parameters are agreed to, and store them in the configuration and parameter tables in the routers. The routers transition to the Learning state as shown the figure. Now, a RF system and network has been established by activating the wireless routers.

In the start up state, chores of the WR are: i) identification of the neighbors of the WR and preparation neighbor list, ii) interference impact, coverage, and other parameter analysis, iii) configuration of LSPs with neighbors, and iv) exchange and negotiation of power and handoff parameters with neighbors. In this way, the WR automatically configures itself for operation in the wireless network. Once these operations are completed, it transitions to the learning state.

2) Learning State: In the learning state, the WR continues to analyze, exchange and negotiate parameters, in order to minimize interference in the wireless network and to ensure that all the operational thresholds are met. The WR transitions into this state from the start-up state when RF power is up, and from operation state when either operational parameters change, or the WR neighbors change, or the operational thresholds are not met. In the learning state, parameters are re-negotiated and re-estimated based on the information given during transition from the operational state. Once operational thresholds are met for a specific period of time, the WR transitions to the operational state.

3) Operational State: In the operational state, the WR continues to monitor its operational thresh-olds periodically or otherwise exchanges information with its WR neighbor to ensure maximum efficiency and minimum RF interference within the wireless network. If the operational thresholds are not met, the wireless router transitions from the operational state back to the learning state for detailed analysis and evaluation of the configuration parameters and reconfiguration, as required, so that the operational thresholds can be met.
Also, if any of the neighboring routers change, affecting the topology of the network, such as a neighboring router failure, or a new router is added to the wireless topology, the router transitions from the operational state to the learning state, to reconfigure itself to suit to the new topology. In addition, if any parameters are changed due to any requests from its neighbors, the WR transitions to the learning state, for analysis and evaluation of operation using the new parameters.

4) Site Down state: The wireless router may enter the site down state from the learning state or the operational state if it requires either scheduled or unscheduled maintenance. Upon power up, the router will again transition back to the start up state for reloading and reconfiguration of the operational parameters. In this way, the wireless routers automatically adjust and account for changing conditions in the network to optimize operation of the network.

Mechanisms to Dynamically Configure the Router | Solutions and Recommendations

The proposed WR has been designed for dynamic configuration of its operational parameters. Configuration parameters of a WR are typically related to the site and technology used. Site parameters may be classified as geo-location, network operation, service configuration, and antenna parameters. The technology specific parameters depend upon whether the CDMA or GSM is supported and include technology-specific site parameters, but may be broadly classified into coverage, spectrum, channel, interference, control, and threshold parameters. At a finer level of detail, site Id, number of sectors/beams, sector/beam ID, latitude and longitude, sector/beam location, maximum radius of influence are typical geo parameters. Similarly, network configuration parameters include network interfaces (e.g. Tl, SONET, T3, etc.), site capacity, and network capacity. In the service configuration, we may have the list of various services supported, and the related directory agent (DA) addresses. The antenna parameters listed on a per sector/beam basis include the antenna type, digitized pattern, horizontal/vertical beam widths, max gain, and mechanical and electrical down tilts.

In the technology parameters class, maximum RTD (round trip delay), PER (packet error rate), FER(frame error rate), and percentages of blocked calls, access failures, dropped calls constitute the threshold parameters subclass. The coverage parameters subclass includes environment (e.g. rural or urban), path loss margin, technology specific hardware losses and gains, RF coverage prediction models, and traffic distribution maps. The spectrum parameters subclass consists of channel bandwidth, channel mask, channel number range, and maximum transmit power per channel. The channel parameters include the number of channels in the range, air capacity/bandwidth, minimum channel spacing, frequency use, frequency grouping, and hopping sequences. The interference parameters include interference thresholds, power control thresholds, channelization and sequencing, channel scheduling algorithms, RF interference prediction models, traffic distribution maps, and adjacent channel interference threshold. The control parameters subclass includes access parameters, intra-technology and inter-technology handoff parameters, and timing parameters.

In the following subsection, we present a very high level procedure by which a WR learns its parameters and configures itself in collaboration with its neighbors. The control logic and the operations performed in each high level state could be quite complex with several states for error paths and exceptions. For example, application of RF or IP discovery protocols in the startup state involves considerable information exchange between a WR and its neighbors.
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