wimax ieee 802.16 m and ieee 802.16 m evaluation methodology document ieee 802.16 protocol architecture and ieee 802.16 and its enhancements
Dr.MohitBansal,Canada,Teacher
Published Date:25-10-2017
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IEEE 802.16m Reference Model
and Protocol Structure
INTRODUCTION
The IEEE 802.16-2009 standard defines a generic reference model where major functional blocks
(i.e.,physicallayer,securitysub-layer,MACcommonpartsub-layer,andservicespecificconvergence
sub-layer)andtheirinterfaces,thepremisesofIEEE802.16entity,andageneralnetworkcontroland
management system are specified. The IEEE 802.16m has modified this reference model by further
classifyingtheMACcommonpartsub-layerfunctionsintotwofunctionalgroups,resultinginamore
structured approach to characterizing the data link layer functions and their interoperation.
Theearlierrevisionsand/oramendmentsoftheIEEE802.16standarddidnotexplicitlydefineany
detailed protocol structure; rather, the functional elements in the specification were implicitly clas-
sified as convergence sub-layer, MAC common part sub-layer, security sub-layer, and physical layer.
While each of these layers and/or sub-layers comprises constituent functions and protocols, no
perspective was provided on how various components were interconnected and interoperated from
a system standpoint. In fact, the IEEE 802.16 standards have never been developed with a system
engineering approach; rather, they specify components and building blocks that can be integrated
(obviously various combinations are potentially possible) to build a working and performing system.
An example is the mobile WiMAX system profiles 1, where a specific set of IEEE 802.16-2009
features were selected to form a mobile broadband wireless access system. In an attempt to improve
theclarityofthepreviousIEEE802.16standardsandtotakeasystematicapproachindevelopmentof
the advanced air interface, IEEE 802.16m has defined a protocol structure and the functional
components are classified into different layers and sub-layers, as well as differentiated based on data-
plane or control-plane categories.
The protocols and functional elements defined by the IEEE 802.16 standard correspond to the
physicalanddatalinklayersoftheOpenSystemInterconnection(OSI)seven-layernetworkreference
model as shown in Figure 3-1.
In the context of protocol structure, we will frequently use the terms “service” and “protocol.” It
must be noted that services and protocols are distinct concepts. A service is a set of primitives or
operationsthatalayerprovidestothelayer(s)withwhichitisinterfaced2.Theservicedefineswhat
operations a layer performs without specifying how the operations are implemented. It is further
relatedtothe interface between twoadjacentlayers. Aprotocol,incontrast,is aset ofrulespresiding
over the format and interpretation of the information/messages that are exchanged by peer entities
within a layer. The entities use protocols to implement their service definitions. Thus, a protocol is
related to the implementation of a service.
61
OSI Seven-Layer Network Model
Application Layer
Presentation Layer
Session Layer
Scope of IEEE 802.16 Standards
Protocols
Transport Layer
Service Specific
Convergence
Network Layer
Sublayer
Data-Link Layer
Medium Access
Control Common Part
Sublayer
Physical Layer
Security Sublayer
Physical Layer
FIGURE 3-1
The mapping of IEEE 802.16 protocol layers to an OSI seven-layer network model
Layer N+1 Layer N+1
SDU PDU
Layer N Layer N Layer N
Services or Functions Protocol Services or Functions
PDU SDU
Layer N-1 Layer N-1
Source Destination
FIGURE 3-2
An illustration of service, protocol, PDU, and SDU concepts 2
AsshowninFigure3-2,aProtocolDataUnit(PDU)isapacketexchangebetweenpeerentitiesof
thesameprotocol layerlocatedat the sourceanddestination. On the downward direction,the PDU is
the data unit generated for the next lower layer. On the upward direction, it is the data unit received
fromthepreviouslowerlayer.AServiceDataUnit(SDU),ontheotherhand,isadataunitexchanged
between two adjacent protocol layers. On the downward direction, the SDU is the data unit received
fromtheprevioushigherlayer.Ontheupwarddirection,itisthedataunitsenttothenexthigherlayer.Network Control and Management System
M-SAPC-SAP
3.1 The IEEE 802.16m reference model 63
This chapter provides a top-down systematic description of IEEE 802.16m reference model and
protocol structure, starting at the most general level and working toward details or specifics of
the protocol layers, their functional constituents and interconnections. An overview of 3GPP LTE
protocol structure is further provided to enable readers to contrast the corresponding protocols and
functionalities.
It must be noted that while the IEEE 802.16 standard does define a generic network reference
model (or a network abstraction model), the mobile WiMAX systems use the specific network
reference model and system architecture that were described in Chapter 2 to achieve interoperability.
Therefore, the network reference model and associated components and interfaces described in
Section 3.1 are only informative, and they should not be interpreted as normative for implementation
and deployment of the IEEE 802.16m systems.
3.1 THE IEEE 802.16M REFERENCE MODEL
Figure 3-3 illustrates the IEEE 802.16 reference model 3. The data link layer of IEEE 802.16
standard comprises three sub-layers. The service-specific convergence sub-layer (CS) provides any
IEEE 802.16 Entity
CS SAP
Service Specific Convergence
Sublayer
(CS)
CS Management/Configuration
MAC SAP
MAC Common Part Sublayer
(MAC CPS)
MAC Management/Configuration
Security Sublayer
Management Information Base
(MIB)
PHY SAP
Physical Layer
(PHY)
PHY Management/Configuration
Data/Control Plane Management Plane
FIGURE 3-3
The IEEE 802.16 reference model 364 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
transformationormappingofnetwork-layerdatapacketsintoMACSDUs.Onthetransmitterside,the
CS receives the data packets through the CS Service Access Point (SAP) and delivers MAC SDUs to
the MAC Common Part Sub-layer (MAC CPS) through the MAC SAP. This includes classifying
network-layer SDUs and associating them with the proper MAC Service Flow Identifiers (SFID) and
Connection Identifiers (CID). The convergence sub-layer also includes payload header suppression
function to compress the higher-layer protocol headers. Multiple CS specifications are provided for
i
interfacing with various network-layer protocols such as Asynchronous Transfer Mode (ATM) and
packet-switched protocols such as IP or Ethernet. The internal format of the CS payload is unique to
theCS,andtheMACCPSisnotrequiredtounderstandtheformatoforparseanyinformationfromthe
CS payload.
The MAC CPS provides the core MAC functionality of system access, bandwidth allocation,
connection establishment, and connection maintenance. It can receive data from the various conver-
gence sub-layers, through the MAC SAP classified into particular MAC connections. An example of
MACCPSservice definitionisgiveninreference3.TheQualityofService(QoS)isfurtherapplied
to the transmission and scheduling of data over the physical layer.
The MAC also contains a separate security sub-layer providing authentication, secure key
exchange, andencryption.Theuserdata,physical layercontrol,andstatisticsaretransferred between
the MAC CPS and the Physical Layer (PHY) via the PHY SAP which is implementation-specific.
The IEEE 802.16physical layer protocols include multiple specifications, defined through several
amendments and revisions, each appropriate for a particular frequency range and application. The
IEEE 802.16 compliant devices include mobile stations or base stations. Given that the IEEE 802.16
devices may be part of a larger network, and therefore would require interfacing with entities for
management and control purposes, a Network Control and Management System (NCMS) abstraction
has been introduced in the IEEE 802.16 standard as a “black box” containing these entities 3. The
NCMS abstraction allows the physical and MAC layers specified in the IEEE 802.16 standard to be
independentofthenetworkarchitecture,thetransportnetwork,andtheprotocolsusedinthebackhaul,
and therefore would allow greater flexibility. The NCMS entity logically exists at both BS and MS
sides of the radio interface. Any necessary inter-BS coordination is coordinated through the NCMS
entityattheBS.AnIEEE802.16entityisdefinedasalogicalentityinanMSorBSthatcomprisesthe
physical and MAC layers on the data, control, and management planes.
The IEEE 802.16f amendment (currently part of IEEE 802.16-2009 standard 3) provided
enhancementstoIEEE802.16-2004standard,definingamanagementinformationbase(MIB),forthe
physical and medium access control layers and the associated management procedures. The
management information base originates from the Open Systems Interconnection Network Manage-
ment Model and is a type of hierarchical database used to manage the devices in a communication
network5,6.Itcomprisesacollectionofobjectsinavirtualdatabaseusedtomanageentitiessuchas
routers and switches in a network.
i
Asynchronous Transfer Mode (ATM) is a packet switching protocol that encodes data into small fixed-sized cells and
provides data link layer services that run over OSI layer 1, differing from other technologies based on packet-switched
networkssuchasIPorEthernet,inwhichvariable-sizedpacketsareused.ATMexploitspropertiesofbothcircuit-switched
andsmallpacket-switchednetworks,makingitsuitableforwideareadatanetworking,aswellasreal-timemediatransport.
ATM uses a connection-oriented model and establishes a virtual circuit between two end-points before the actual data
exchange begins 4.Management Plane
Data/Control Plane
3.1 The IEEE 802.16m reference model 65
ii
TheIEEE802.16standarddescribestheuseofaSimpleNetworkManagementProtocol(SNMP),
i.e., an IETF protocol suite, as the network management reference model. The standard consists of
aNetworkManagementSystem(NMS),managednodes,andaserviceflowdatabase.TheBSandMS
managednodescollectandstorethemanagedobjectsintheformofWirelessMANInterfaceMIBand
Device MIB that aremadeavailabletonetworkmanagement systemviamanagement protocols, such
as SNMP. A Network Control System contains the service flow and the associated Quality of Service
informationthathavetobeprovidedtoBSwhenanMSentersintothenetwork.TheControlSAP(C-
SAP)andManagementSAP(M-SAP)interfacethecontrolandmanagement planefunctionswiththe
upperlayers.TheNCMSentitypresentswithineachMS.TheNCMSisalayer-independententitythat
may be viewed as a management entity or control entity. Generic system management entities can
perform functions through NCMS and standard management protocols can be implemented in the
NCMS. If the secondary management connection does not exist, the SNMP messages, or other
management protocol messages, may go through another interface in the customer premise or on
a transport connection over the air interface. Figure 3-4 describes a simplified network reference
Network Control and Management Network Control and Management
System (NCMS) System (NCMS)
IEEE 802.16
C-SAP M-SAP C-SAP M-SAP
Air-Interface
IEEE 802.16 Entity IEEE 802.16 Entity
Data/Control Planes
Mobile Station (MS) Base Station (BS)
FIGURE 3-4
The IEEE 802.16 generic network reference model 3
ii
An SNMP-managed network consists of three key components: (1) a managed device; (2) an agent; and (3) a network
managementsystem.AmanageddeviceisanetworknodethatcontainsanSNMPagentandresidesinamanagednetwork.
Managed devices collect and store management information and make this information available to NMSs using SNMP.
Managed devices, sometimes called network elements, can be any type of device including, but not limited to, routers,
access servers, switches, etc. An agent is a network-management software module that resides in a managed device. An
agent has local knowledge of management information and translates that information into a form compatiblewith SNMP.
A network management system executes applications that monitor and control managed devices. The NMSs provide the
processing and memory resources required for network management. One or more NMSs may exist on any managed
network 7,8.NCMS-N
Network Interfaces
Control and Management Interface
NCMS-E
M-SAPC-SAP
66 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
model.MultiplemobilestationsmaybeattachedtoaBS.TheMScommunicatestotheBSovertheair
interface using a primary management connection, basic connection or a secondary management
connection 3. The latter connection types have been replaced with new connection types in IEEE
802.16m standard 12.
3.1.1 The MS and BS Interface
iii
The MAC management PDUs that are exchanged over the primary management connection can
trigger, or are triggered by, primitives that are exchanged over either the C-SAP or the M-SAP,
depending on the particular management or control operation. The messages that are exchanged over
the secondary management connection can trigger or are triggered by primitives that are exchanged
overtheM-SAP.ThisinterfaceisasetofSAPbetweenanIEEE802.16entityandNCMSasshownin
Figure 3-5. It consists of two parts: the M-SAP is used for delay-tolerant management-plane primi-
tives; and the C-SAP is used for delay-sensitive control-plane primitives that support handovers,
Scope of IEEE 802.16 Standard
CS SAP
Service Specific Convergence
Sublayer (CS)
CS Management/Configuration
MAC SAP
MAC Common Part Sublayer
(MAC CPS)
MAC Management/Configuration
Security Sublayer
Management Information
Base (MIB)
PHY SAP
Physical Layer
(PHY)
PHY Management/Configuration
Control Plane/Data Plane Management Plane
Other Network
Embodyment of IEEE 802.16 Entity
Entities
FIGURE 3-5
Partitioning of the IEEE 802.16 network control and management system 3
iii
A management connection is used for transporting MAC management messages or standards-based messages. The
primary management connection is established during network entry and is used to transport delay-tolerant MAC
management messages. The secondary management connection may be established during MS registration that is used to
transport standards-based messages; e.g., SNMP, DHCP messages.3.1 The IEEE 802.16m reference model 67
security context management, radio resource management, and low power operations such as idle
mode and paging functions.
3.1.2 Network Control and Management System
TheNetworkControlandManagementSystemisnotpartoftheIEEE802.16standards,andistreated
asa“blackbox.”Itmaybedistributedwithcomponentsresidingondifferentnodesinanetwork.Part
of the NCMS may be physically collocated with the IEEE 802.16 entity referred to as NCMS-E. The
remaining part of the NCMS may be physically distributed across one or more network entities. This
part of the NCMS is referred to as NCMS-N. Figure 3-5 shows the partitioning of the NCMS into
NCMS-E and NCMS-N. The NCMS-E may have its own software platform and network protocol
implementation,allowingittocommunicatewithexternalentitiesintheNCMS-N.TheNCMS-Emay
provide an SNMPAgent compliant to IETF RFC3418 13 and the SNMP/TCP/IP protocol stack, to
allow for interactions with an SNMP manager. The NCMS-E may provide an Object Request Broker
andimplementaprotocolstacktointeractwithcomponentsonothernetworkentitieswithinNCMS-N
iv
based on the CORBA architecture. The messages available to a manager in the NCMS-N are
v
specified using Interface Description Language (IDL). These messages encapsulate the interactions
vi
with the MIB. The IEEE 802.16 entity can be managed through Web Services. 11
Thedecomposition ofNetworkControl and Management Systemis depictedin Figure 3-6. These
entities may be centrally located or distributed across the network. The exact functionality of these
entities and their services is outside the scope of the IEEE 802.16 standard, but is shown here for
illustration purposes and to allow description of the management and control procedures. The NCMS
service manifestations on the MS and BS may have different configurations and functions.
TheIEEE802.16mreferencemodelisverysimilartothatoftheIEEE802.16-2009standard,with
the exception of soft classification of MAC common part sub-layer into radio resource control and
management and medium access control functions. As shown in Figure 3-7, this functional parti-
tioningislogical, i.e.,noSAP isrequiredbetween thetwoclassesoffunctions andnoadditional sub-
headersareappendedtotheSDUs.Furthermore,thefunctionalelementsonthedataandcontrolpaths
areexplicitlyclassifiedintodata-andcontrol-planefunctions.Whilesimilarfunctionalitiesexistinthe
IEEE 802.16-2009 standard, the functions and protocols are not explicitly categorized in the legacy
standard except explicit separation of PHY, MAC CPS, and CS functions in the specification 3.
The categorization of the functions based on functional characteristics and relative position in the
data/signaling processing path would ease analogy, and contrast with other radio access technologies
iv
The Common Object Requesting Broker Architecture (CORBA) is a standard defined by the Object Management Group
that enables software components written in multiple computer languages and running on multiple computers to work
together 9.
v
An Interface Description Language (IDL) is a specification language used to describe a software component’s interface.
IDLs describe an interface in a language-independent way, enabling communication between software components that do
not share a language; e.g., between components written in Cþþ and Java 10.
vi
AWeb Service is a software system designed to support interoperable machine-to-machine interaction over a network. It
has an interface described in a machine-processable format. Other systems interact with the web service in a manner
prescribed by its description using SOAP-messages (Simple Object Access Protocol is a lightweight protocol intended for
exchanging structured information in a decentralized, distributed environment) typically conveyed using HTTP with an
XML serialization in conjunction with other web-related standards.Network Control and Management System
M-SAPC-SAP
68 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
Network Control and Management System
Mobility Management
AAA Services Security Services
Services
Radio Resource Service Flow Paging and Idle Mode
Management Services Management Services Services
Multicast Broadcast Location Based Services Media Independent
Services Management Management Handover Functions
Subscriber Station
Network Management
Management
Services
(Only MS Side)
FIGURE 3-6
Decomposition of the network control and management system 3
IEEE 802.16 Entity
CS SAP
Radio Resource Service Specific
Control and Convergence
Management Sublayer
Functional Group (CS)
MAC SAP
CS Management/Configuration
Medium Access Control Functional
MAC CPS
Group
MAC Management/Configuration
Security Sublayer
Management Information Base
(MIB)
PHY SAP
Physical Layer
(PHY)
PHY Management/Configuration
Control Plane Data Plane Management Plane
FIGURE 3-7
The IEEE 802.16m reference model 123.1 The IEEE 802.16m reference model 69
suchas3GPPLTE/LTE-Advancedthathavebeendesignedbasedonsimilarstructuredprotocoldesign
methodology. Furthermore, the structured functional/protocol design in IEEE 802.16m would elimi-
nate the inherent complexity and ambiguity of studying, understanding, and implementing the legacy
standard.
Itmustbenotedthattherearenew,modifiedorextendedfunctionsandprotocolsthatareclassified
undergenericclassesofPHY,MACCPS,andCSinIEEE802.16m,wheretherearenocounterpartsin
the legacy standard. Therefore, similarity of the reference models should not be interpreted as func-
tional compatibility at the service access points. The backward compatibility of the IEEE 802.16m
with the legacy standard ensures that non-compatible functions/protocols are not utilized in the time
intervals where legacy base stations and mobile stations are supported in the network.
3.1.3 Data-Plane
TheMACandPHYfunctionsoftheIEEE802.16mcanbeclassifiedintothreecategoriesnamelydata-
plane, control-plane, and management-plane. The data-plane (alternatively known as user-plane)
comprises functions in the user data processing path, such as service flow classification and header
compression,aswellasMACandPHYdatapacketprocessingandencryptionfunctions.Asshownin
Figure3-8,theIEEE802.16mdata-planeentitycomprisestheservicespecificConvergenceSub-layer,
IEEE 802.16m Data-Plane Entity
CS SAP
Service Specific Convergence
Sublayer
(CS)
MAC SAP
Medium Access Control Functional
Group
(Data Plane Functions)
Security Sublayer
(Data Plane Security)
PHY SAP
Physical Layer
(PHY)
FIGURE 3-8
The IEEE 802.16m data-plane entity 1270 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
MACfunctionalgroup,security,andphysicallayerprotocolscorrespondingtodata-planeuserpacket
processing.TheMACandPHYSAPs,whileconceptuallythesameasthosespecifiedbyIEEE802.16-
2009 standard, have different manifestation due to the new and/or modified MAC and PHY features
introduced in the IEEE 802.16m standard. There is no significant change in CS SAP relative to that
specified in the IEEE 802.16-2009 standard 3.
The CS provides a mapping of external network data formats (e.g., IP layer packets, ATM cells)
received through CS SAP into MAC SDUs that are delivered to the MAC CPS via MAC SAP. This
includesclassifyingexternalnetworkSDUsandassociatingthemwithaproperServiceFlowIdentifier
andConnectionIdentifier.AServiceFlow(SF)isaMACtransportservicethatprovidesunidirectional
transport of packets inthe downlink oruplink 14. It is identified by a 32-bit SFID. A service flow is
characterizedbyasetofQoSparameters,i.e.,aparametersetassociatedwithaserviceflowidentifier
containing traffic parameters which define scheduling behavior of uplink or downlink service flows
associated with transport connections. An admitted and active service flow is uniquely mapped to
aCID.NotethattheIEEE802.16standardsupportstwophaseactivationmodel.i.e.,theresourcesfor
a service are first admitted or reserved and once the BS and MS negotiations are completed, the
resources are activated 3.
TheGenericPacketCS(GPCS)isanetworklayerprotocol-agnosticpacketconvergencesub-layer
thatsupportsmultiplenetworkprotocolsoverIEEE802.16airinterface.TheGPCSprovidesageneric
packet convergence sub-layer. This layer uses the MAC SAP and exposes a SAP to GPCS applica-
tions.TheGPCSdoesnotredefineorreplaceotherconvergencesub-layers.Instead,itprovidesaSAP
that is not protocol specific. With GPCS, packet parsing occurs above GPCS. The results of packet
parsing are classification parameters provided to the GPCS SAP for parameterized classification;
however, upper layer packet parsing is left to the GPCS application. With GPCS, the upper layer
protocol that is immediately above the IEEE 802.16 GPCS is identified by a parameter known as
GPCSprotocoltype.TheGPCSprotocoltypeis includedinservice flowmanagementprimitivesand
connectionestablishmentmessages.TheGPCSdefinesasetofSAPparametersastheresultofupper
layer packet parsing. These are passed from upper layer to the GPCS in addition to the data packet.
The SAP parameters include SFID, the MS MAC Address, data, and length. The GPCS allows
multiplexing of multiple layer protocol types (e.g., IPv4, IPv6, and Ethernet) over the same IEEE
802.16 MAC connection. It is outside the scope of the GPCS protocol to specify how the upper layer
multiplexes and de-multiplexes multiple protocol data packets over an IEEE 802.16 connection or
service flow 3.
In multimedia streaming applications, the overhead of Internet Protocol (IP) 15, User Datagram
Protocol(UDP)16,andReal-timeTransportProtocol(RTP)17,18payloadheadersare40bytesfor
IPv4(or60bytesforIPv619).Forvoice-over-IP,thiscorrespondstoapproximately60%ofthetotal
amountofencodedvoicedata(e.g.,theRTPpayloadof3GPPAdaptiveMulti-Rate12.2kbpsfull-rate
codecconsistsof33bytes20).Suchlargeoverheadsmaybetolerableinwiredlinkswherecapacity
is often not an issue, but are excessive for wireless systems where bandwidth is scarce. The IEEE
802.16 standard defines a native header compression algorithm that is part of the convergence sub-
layer. The Payload Header Suppression (PHS) defined in the IEEE 802.16 standard compresses the
repetitiveorredundantpartsofthepayloadheaderreceivedfromnetworklayer.ThePHSoperationis
based on the PHS rules, which provide all the parameters corresponding to header suppression of the
SDU. Other standard header compression algorithms, such as Robust Header Compression (RoHC)
defined by IETF 21, are also supported.3.1 The IEEE 802.16m reference model 71
TheRoHCschememaybeusedasanalternativetoPHStocompresstheRTP/UDP/IPheaderofan
IP packet. When RoHC is enabled for a service flow, the service flow constitutes what in IETF RFC
3095 is referred to as a RoHC channel 21,3. Two service flows cannot share an RoHC channel, and
two RoHC channels cannot share the same service flow. On a service flow for which RoHC has been
enabled, all of the IP packet passes through the RoHC compressor on the transmitter side and the
decompressoronthereceiverside.ThesupportofRoHCisnegotiatedbetweentheBSandMSduring
capability negotiation 3.
The data-plane part of MAC CPS includes functions such as Automatic Repeat reQuest (ARQ),
Packet Fragmentation/Packing, MAC PDU formation and encryption. The scheduler on the BS side
allocates radio resources and multiplexes the users, and selects the appropriate MIMO mode,
modulation and coding scheme based on the measurement reports that are received from the mobile
stations.TheARQisanerrorcontrolmechanismatdatalinklayerwherethereceivermayrequestthe
transmitter to resend a block of data that was erroneously detected or not received. An ARQ block is
a distinct unit of data that is carried on an ARQ-enabled connection. Such a data unit is assigned
a sequence number and is managed as a distinct entity by the ARQ state machines. The ARQ block
size is a parameter that is negotiated during connection establishment. The ARQ mechanism may be
disabled for some delay sensitive applications such as VoIP. Fragmentation is a process in which
a MAC SDU is divided into one or more MAC SDU fragments. Packing is a process where multiple
MAC SDUs are packed into a single MAC PDU payload. Both processes may be initiated by either
a BS for a downlink connection or an MS for an uplink connection. Several MAC PDUs may be
concatenated into a single transmission in the downlink or uplink.
The MAC PDUs containing user data are processed by the physical layer for over-the-air trans-
mission.Itmustbenotedthatthephysicallayerprocessingoftheusertrafficcanbedifferentinterms
of the permissible MIMO modes or modulation and coding schemes that are used.
3.1.4 Control-Plane
A set of Layer 2 control functions are needed to support various radio resource configuration,
coordination,signaling,andmanagement.Thissetoffunctionsiscollectivelyreferredtoascontrol-
plane functions. The IEEE 802.16m control-plane entity comprises Radio Resource Control and
Management (RRCM), MAC functional group, and physical layer protocols corresponding to
control path. The RRCM functional class includes all control and management functions such as
network entry/re-entry management, paging and idle mode management, multicast and broadcast
service, etc. This group of functions is also known as Radio Resource Control (RRC) in other air
interface standards such as 3GPP LTE. The MAC functional group consists of functions that
perform physical layer control and signaling, scheduling services, QoS, etc. This functional group
corresponds to Radio Link Control (RLC) and MAC layers in other air interface standards such as
3GPP LTE.
Figure 3-9 illustrates the IEEE 802.16m control-plane entity. As shown in this figure, the RRCM
performscontrolandmanagementoflower-layerfunctions.Thecontrolinformationiscommunicated
with the mobile station via MAC management messages. The underlying functional elements of the
RRCM sub-layer will be described in Section 3.2.
The security sub-layer in Figure 3-9 is shown with dotted line, since the IEEE 802.16m
selectively encrypts and protects unicast MAC management messages. If the selective72 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
IEEE 802.16m Control-Plane Entity
Radio Resource Control and
Management Functional Group
(RRCM)
Medium Access Control Functional
Group
(Control Plane Functions)
Security Sublayer
(Control Plane Security)
PHY SAP
Physical Layer
(PHY)
FIGURE 3-9
The IEEE 802.16m control-plane entity 12
confidentiality protection is utilized, the negotiated keying materials and cipher suites are used to
encrypt the management messages. There are three levels of selective confidentiality protection
appliedtoMACmanagementmessages in the IEEE 802.16m: (1) no protection where the MS and
BShavenosharedsecuritycontextorprotectionisnotrequired,thenthemanagementmessagesare
neither encrypted nor authenticated. Management messages before the authorization phase also fall
vii
into this category; (2) cipher-based message authentication code (CMAC) integrity protection
protects the integrity of the entire MAC management message; and (3) advanced encryption stan-
viii
dard-based (AES-CCM) authentication/encryption protects the integrity of payload and MAC
header 3.
vii
A cipher-basedMAC (CMAC)is ablock cipher-basedmessage/code authentication algorithm. It maybeused to provide
assurance ofthe authenticity and integrityof user payloads. AES-CMACprovidesstronger assurance of data integritythan
a checksum or an error-detecting code. The verification of a checksum or an error-detecting code detects only accidental
modifications of the data, while CMAC is designed to detect intentional, unauthorized modifications of the data, as well as
accidental modifications.
viii
The counter with CBC-MAC (CCM), as defined in IETF RFC 3610, is a generic authenticated encryption block cipher
mode. CCM is only defined for use with 128-bit block ciphers, such as AES. It is an authenticated encryption algorithm
designed to provide both authentication and privacy.Network Control and Management System
M-SAPC-SAP
3.1 The IEEE 802.16m reference model 73
3.1.5 Management-Plane
Amanagement-planeisalsodefinedforexternalmanagementandsystemconfiguration.Therefore,all
managementandprotocolconfigurationentities,aswellasmanagementinformationbase,fallintothe
management-planecategory.DefinitionofmanagementinformationbasesareoutofscopeoftheIEEE
802.16mstandard.AsshowninFigure3-10,themanagemententityandthemanagementinformation
bases contained in the management-plane, configure and manage the functional entities in the data-
and control-plane protocol layers. The IEEE 802.16 specification includes control and management
SAPs as part of the management-plane that exposecontrol-plane and management-plane functions to
upper layers. Management-plane primitives and the C-SAP are used for more time sensitive control-
plane primitives that support handovers, security context management, radio resource management,
and low power system operations.
In addition, under the IEEE 802.16 standard, a user can be associated with a number of service
flows, each characterized with different QoS parameters. This information is provisioned in
a subscriber management system (e.g., AAA database) or a policy server. There are two service
models:(1) static service model,where thesubscriberstation isnot allowedtochangetheparameters
ofprovisionedserviceflowsorcreatenewserviceflowsdynamically;and(2)dynamicservicemodel,
where an MS or BS may create, modify or delete service flows dynamically. In the latter case,
IEEE 802.16 Management Plane Entity
CS Management/Configuration
MAC Management/Configuration
Security Management/Configuration
Management Information Base
(MIB)
PHY Management/Configuration
FIGURE 3-10
The IEEE 802.16 management-plane entity 374 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
adynamicserviceflowrequestisevaluatedagainsttheprovisionedinformationtodecidewhetherthe
request could be authorized. More precisely, the following steps are provisioned in the IEEE 802.16
specification for dynamic service flow creation 22:
1. PermittedserviceflowsandassociatedQoSparametersareprovisionedforeachsubscriberviathe
management plane (management entity).
2. A service flow request initiated bytheMS or BSis evaluatedagainstthe provisionedinformation,
and the service flow is created if permissible.
3. Aserviceflowthuscreatedtransitionstoanadmitted,andfinallytoanactive,stateduetoBSaction
(this is possible under both static and dynamic service models). Transition to the admitted state
involves the invocation of admission control in the BS and (soft) resource reservation, and
transition to the active state involves actual resource assignment for the service flow. The
service flow can directly transit from provisioned state to active state without going through
admitted state.
4. Aserviceflowcanalsotransitioninthereversefromanactivetoanadmittedtoaprovisionedstate.
5. A dynamically created service flow may also be modified or deleted.
As mentioned earlier, management information bases are collections of various network objects that
are operated with the use of a Simple Network Management Protocol or SNMP 8,13. The exact
structure of the objects included in the management information base will depend on the configu-
ration of the particular SNMP. However, additional extensions can allow for the addition of new
objects outside the initial structure. Both the initial management information base and its extensions
can be related to specific functions within a network. Some MIBs may be related to the definition of
the domain name system, while other extensions may be associated with network objects like the
fiber distributed data interface. While the initial management information base is usually defined as
part of the SNMP, the extensions are generally set up as part of the basic management information
base.
The Subscriber Station Management Primitives are a set of primitives to manage the status of
mobile station. A management entity in the NCMS can change the status of mobile terminal. Those
primitivesarealsousedtonotifytheNCMSofinformationoreventswhicharerelatedtothestatusof
the mobile terminal. The NCMS is a layer-independent entity that may be viewed as a management
entity or control entity.
3.1.6 Service Access Point
A Service Access Point is defined as a reference point in a protocol stack where the services of
a layer are available to its immediately neighboring layer. In other words, a SAP is a mapping
between services of two neighboring layers. There are a number of SAPs in the IEEE 802.16
reference model (see Figure 3-7) that interface the adjacent protocol layers including PHY, MAC,
and CS SAPs. The Management SAP may include primitives related to System configuration,
Monitoring statistics, Notifications/Triggers, and Multi-mode interface management. The NCMS
interacts with the MIB through the M-SAP. The Control SAP may include, but is not limited to,
primitivesrelatedtohandovers(e.g.,notificationofhandoverrequestfromMS),idlemodemobility
management (e.g., mobile station entering idle mode), subscriber and session management
(e.g., mobile station requesting session set-up), radio resource management, AAA server signaling3.1 The IEEE 802.16m reference model 75
ix x
(e.g., Extensible Authentication Protocol payloads), Media Independent Handover (MIH)
services,andlocationdetectionandreportingcapability.Unlike3GPPLTE,theIEEE802.16mdoes
not explicitly define logical, transport, and physical channels (although the functionalities exist in
the air interface protocols). In that case, the mapping between logical to transport and transport to
physical channels would determine the SAPs between the corresponding layers.
3.1.7 Media-Independent Handover Reference Model for IEEE 802.16
The IEEE 802.21-2008 standard provides link-layer intelligence and other related network informa-
tiontoupperlayerstooptimizehandoversbetweenheterogeneousnetworks23.Thisincludesmedia
types specified by 3GPP, 3GPP2, and both wired and wireless media in the IEEE 802 family of
standards. In the IEEE 802.21-2008 standard, media refers to the method or mode of accessing
a telecommunication system (e.g., cable, radio, satellite), as opposed to sensory aspects of commu-
nication (e.g., audio, video). The standard addresses the support of handovers for both mobile and
stationary users. For mobile users, handovers can occur when wireless link conditions change due to
the users’ movement. For the stationary user, handovers become imminent when the surrounding
networkenvironmentchanges,makingonenetworkmoreattractivethananother.Asanexample,when
making anetwork transition duringaphone call, thehandover proceduresshould beexecuted insuch
a way that any perceptible interruption to the conversation will be minimized. The standard supports
cooperativeuseofinformationavailableatthemobilenodeandwithinthenetworkinfrastructure.The
mobilenodeiswell-positionedtodetectavailablenetworks.Thenetworkinfrastructureiswell-suited
to store overall network information, such as neighborhood cell lists, location of mobile nodes, and
higher layer service availability. Both the mobile node and the network make decisions about
connectivity. In general, both the mobile node and the network points of attachment (such as base
stationsandaccesspoints)canbemulti-modal(i.e.,capableofsupportingmultipleradiostandardsand
simultaneously supporting connections on more than one radio interface).
Figure3-11showstheMediaIndependentHandoverFunction(MIHF),i.e.,afunctionthatrealizes
MIH services, for IEEE 802.16 based systems. The M-SAP and C-SAP are common between the
MIHF and Network Control and Management System. The M-SAP specifies the interface between
the MIHF and the management plane and allows MIHF payload to be encapsulated in management
messages (such as MOB_MIH-MSG defined in the IEEE 802.16-2009 standard 3). The primitives
specified by M-SAP are used by a mobile node to transfer packets to a base station, both before and
after it has completed the network entry procedures. The C-SAP specifies the interface between the
MIHFandcontrol-plane.M-SAPandC-SAPalsotransportMIHmessagestopeerMIHFentities.The
CS-SAP is used to transfer packets from higher layer protocol entities after appropriate connections
havebeenestablishedwiththenetwork.TheMIH-SAPspecifiestheinterfaceoftheMIHFwithother
higherlayerentitiessuchastransportlayer,handoverpolicyengine,andLayer3mobilityprotocols.In
this model, C-SAP and M-SAP provide link services defined by MIH-LINK-SAP; C-SAP provides
servicesbeforenetworkentry;whileCS-SAPprovidesservicesoverthedata-planeafternetworkentry.
ix
Extensible Authentication Protocol (EAP), as defined by IETF RFC 3748 and updated by IETF RFC 5247, is a universal
authentication framework commonly used in wireless networks and point-to-point connections 24.
x
Media Independent Handover (MIH) is a standard developed by the IEEE 802.21 to enable handover and interoperability
between heterogeneous network types including both 802 and non-802 networks 23.MIH-SAP
M-SAPC-SAP
76 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
Layer 3 Mobility Protocols
CS SAP
Service Specific Convergence
Sublayer
(CS)
CS Management/Configuration
MAC SAP
Media
MAC Common Part Sublayer
Independent
(MAC CPS)
Handover
Function
(MIHF)
MAC Management/Configuration
MIH event
Security Sublayer
service
Management Information Base
MIH
command
(MIB)
service
PHY SAP
MIH
information
service
Physical Layer
(PHY)
PHY Management/Configuration
Data/Control Plane Management Plane
FIGURE 3-11
MIH reference model for the IEEE 802.16 standard 23
3.2 THE IEEE 802.16M PROTOCOL STRUCTURE
In this section, we further examine the functional elements of each protocol layer and their interac-
tions. The 802.16m MAC common part sub-layer functions are classified into radio resource control
and management functional group and medium access control functional group. The control-plane
functions and data-plane functions are also separately classified. This would allow more organized,
efficient, and structured method for specifying the MAC services in the IEEE 802.16m standard
specification. As shown in Figure 3-12, the radio resource control and management functional group
comprises several functional blocks including:
Radioresourcemanagementblockadjustsradionetworkparametersrelatedtothetrafficload,and
also includes the functions of load control (load balancing), admission control, and interference
control;Layer 3 Layer 2 Layer 1
3.2 The IEEE 802.16m protocol structure 77
Network Layer
Management SAP and Control SAP
CS-SAP
System
Location
Relay Radio Resource
configuration
Convergence Sublayer
Functions Management management
management
Mobility Idle Mode
MBS
Multi-Carrier
Management
Management
Classification
Service flow and
Security
Network-entry
Connection
Self Organization
Header
Management management
Management
suppression
Radio Resource Control and Management (RRCM)
MAC SAP
Fragmentation/Packing
Medium Access Control (MAC)
ARQ
Multi Radio Sleep Mode Scheduling and
QoS
Coexistence Management Resource Multiplexing
MAC PDU formation
PHYControl
Control
Link Adaptation Encryption
Data Forwarding
Interference
Signaling
Ranging (CQI, HARQ, power
Management
control)
Control-Plane Data-Plane
PHY Protocol (FEC Coding, Signal Mapping, Modulation, MIMO processing, etc.)
Physical Layer
FIGURE 3-12
The IEEE 802.16m general protocol stack 12
MobilitymanagementblockscansneighborBSsanddecideswhetherMSshouldperformhandover
operation;
Network-entry management block controls initialization and access procedures and generates
management messages during initialization and access procedures;
Location management block supports location based service (LBS), generates messages including
the LBS information, and manages location update operation during idle mode;
Idlemodemanagementblockcontrolsidlemodeoperation,andgeneratesthepagingadvertisement
message based on paging message from paging controller in the core network;
Securitymanagementblockperformskeymanagementforsecurecommunication.Usingmanaged
key, traffic encryption/decryption and authentication are performed;
Systemconfigurationmanagementblockmanagessystemconfigurationparameters,andgenerates
broadcast control messages such as superframe headers;78 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
Multicast and broadcast service (MBS) block controls and generates management messages and
data associated with MBS;
Service flow and connection management block allocates Station Identifier (STID) and Flow
Identifiers (FIDs) during access/handover service flow creation procedures.
The medium access control functional group, on the control plane, includes functional blocks which
are related to physical layer and link controls such as:
PHY control block performs PHY signaling such as ranging, channel quality measurement/
feedback (CQI), and HARQ ACK or NACK signaling;
Control signaling block generates resource allocation messages such as advanced medium access
protocol, as well as specific control signaling messages;
Sleepmodemanagementblockhandlessleepmodeoperationandgeneratesmanagementmessages
related to sleep operation, and may communicate with the scheduler block in order to operate
properly according to sleep period;
Quality-of-service block performs rate control based on QoS input parameters from connection
management function for each connection;
Schedulingandresourcemultiplexingblockschedulesandmultiplexespacketsbasedonproperties
of connections.
The MAC functional group on the data-plane includes functional blocks such as:
Fragmentation/packing block performs fragmentation or packing of MAC Service Data Units
(MSDU) based on input from the scheduling and resource multiplexing block;
Automatic Repeat Request block performs MAC ARQ function. For ARQ-enabled connections,
a logical ARQ block is generated from fragmented or packed MSDUs of the same flow and
sequentially numbered;
MAC protocol data unit formation block constructs MAC PDU (MPDU) such that BS/MS can
transmit user traffic or management messages into PHY channels.
The IEEE 802.16m protocol structure is similar to that of the IEEE 802.16, with some additional
functional blocks in the control-plane for new features including the following:
Relay functions enable relay functionalities and packet routing in relay networks.
Self organization and self-optimization functions enable home BS or femto-cells and plug-
xi
and-play form of operation for indoor BS (i.e., femto-cell ).
Multi-carrier functions enable control and operation of a number of adjacent or non-adjacent RF
carriers (i.e., virtual wideband operation) where the RF carriers can be assigned to unicast and/
or multicast and broadcast services. A single MAC instantiation will be used to control several
physical layers. The mobile terminal is not required to support multi-carrier operation. However,
if it does support multi-carrier operation, it may receive control and signaling, broadcast, and
synchronization channels through a primary carrier and traffic assignments (or services) via the
secondary carriers.
xi
Femto-cells are low-power wireless access points that operate in licensed spectrum to connect standard mobile devices to
a mobile operator’s network using residential DSL or cable broadband connections 25,26.3.2 The IEEE 802.16m protocol structure 79
IEEE 802.16m
BS
Air Interface
Multi-Radio Device
IEEE
Radio i Radio i Radio j Radio j
802.16m
Access Point Device Device Access Point
MS
inter-radio interface
FIGURE 3-13
A generic multi-radio coexistence model 12
Multi-radio coexistence functions in IEEE 802.16m enable the MS to generate MAC
management messages in order to report information on its collocated radio activities, and
enable the BS to generate MAC management messages to respond with the appropriate
actions to support multi-radio coexistence operation. Furthermore, the multi-radio coexistence
functional block at the BS communicates with the scheduler functional block to assist proper
scheduling of the MS according to the reported collocated coexistence activities. The multi-
radio coexistence function is independent of the sleep mode operation to enable optimal
power efficiency with a high level of coexistence support. However, when sleep mode
provides sufficient collocated coexistence support, the multi-radio coexistence function may
not be used (see Figure 3-13).
Interference management functions are used to manage the inter-cell/sector interference effects.
The procedures include MAC layer functions (e.g., interference measurement/assessment reports
sent via MAC signaling and interference mitigation by scheduling and flexible frequency reuse),
and PHY functions (e.g., transmit power control, interference randomization, interference
cancellation, interference measurement, transmit beamforming/precoding). The inter-BS
coordination functions coordinate the operation of multiple base stations by exchanging
information, about interference statistics between the base stations via core-network signaling.
3.2.1 Data-Plane and Control-Plane Functions in Base Stations
and Mobile Stations
Figure 3-14 shows the user data processing path at the BS and MS. As shown in the figure, the
user data traverses the path from network layer to physical layer and vice versa. In the transmitter
side, a network layer packet is processed by the convergence sub-layer, the ARQ function (if
enabled), the fragmentation/packing function, and the MAC PDU formation function, to form
the MAC PDU to be sent to the physical layer for processing. In the receiver side, a physical
layer SDU is processed by MAC PDU formation function, the fragmentation/packing function,80 CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure
Network Layer
Management SAP and Control SAP
Radio Resource Control and Management (RRCM)
CS SAP
System
Convergence Sublayer
Relay Radio Resource Location
Configuration
Management
Functions Management
Management
Service Flow
Classification
Idle Mode
Mobility
E-MBS
Multi-Carrier
Management
Management
Header
Service flow and
Suppression
Network-entry Security
Connection
Self Organization
Management
Management
Management
MAC SAP
Scheduling and Resource Multiplexing
Fragmentation/Packing
ARQ
Multi Radio Sleep Mode
QoS
Coexistence Management
PHYControl
MAC PDU Formation
Control
Link Adaptation
Data Forwarding
Interference
Signaling
Ranging (CQI, HARQ, power
Management
control)
Encryption
HARQ/CQI
Ranging
Medium Access Control (MAC)
Feedback
PHY SAP
PHY Protocol (FEC Coding, Signal Mapping, Modulation, MIMO processing, etc.)
Physical Layer
Control-Plane Data-Plane
Control Primitives between MAC CPS Functions
Control Messages/Signaling (Control Plane)
Data Path (Data Plane)
FIGURE 3-14
Signal flow graph in data- and control-planes 12
the ARQ function (if enabled), and the convergence sub-layer function, to form the network
layer packets. The control primitives between the MAC CPS functions and between the
MAC CPS and PHY that are related to the processing of user traffic data are also shown in
Figure 3-14.
The control-plane signaling and processing flow graph at the BS and the MS are shown in
Figure 3-14. In the transmitter side, the flow of control primitives from control-plane functions to
data-plane functions and processing of control-plane signals by data-plane functions in order to
L1 L2 L3
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