WO2002013429A1 - COMMUNICATIONS PROTOCOL FOR WIRELESS LAN HARMONIZING THE IEEE 802.11a AND ETSI HiPerLAN/2 STANDARDS - Google Patents
COMMUNICATIONS PROTOCOL FOR WIRELESS LAN HARMONIZING THE IEEE 802.11a AND ETSI HiPerLAN/2 STANDARDS Download PDFInfo
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- WO2002013429A1 WO2002013429A1 PCT/US2001/021796 US0121796W WO0213429A1 WO 2002013429 A1 WO2002013429 A1 WO 2002013429A1 US 0121796 W US0121796 W US 0121796W WO 0213429 A1 WO0213429 A1 WO 0213429A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/04—Scheduled or contention-free access
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/14—Spectrum sharing arrangements between different networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/02—Terminal devices
- H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
Definitions
- the invention relates to wireless communications and, more particularly, to a communications protocol (standard) for wireless local area network (WLAN) applications, taking into account the IEEE 802.11a standard and the ETSI HiPerLAN/2 standard.
- WLAN wireless local area network
- a local area network is a network of independent computers, usually confined to a geographic area, such as a single building or a college campus.
- LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people.
- the development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.
- Ethernet is the most popular physical layer LAN technology in use today.
- the Institute for Electrical and Electronic Engineers (IEEE) defines the Ethernet standard as IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network as well as specifying how elements in an Ethernet network interact with one another. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently.
- Ethernet uses Collision Sense Multiple Access with Collision Detection (CSMA/CD).
- CSMA/CD Collision Sense Multiple Access with Collision Detection
- an Ethernet station When an Ethernet station is ready to transmit, it checks for the presence of a signal on the cable. If no signal is present then the station begins transmission, however if a signal is already present then the station delays transmission until the cable is not in use. If two stations detect an idle cable and at the same time transmit data, then a collision occurs. The two stations involved with the collision lay off transmitting again for a time interval which is randomly selected. If the collision occurs again, then the time interval is doubled, and if the collision happens repeatedly, an error is reported.
- the 'Ether' part of Ethernet denotes that the system is not meant to be restricted for use on only one medium type. Copper cables, fibre cables and radio waves can be used.
- a wireless LAN is a data transmission system designed to provide location-independent network access between computing devices by using radio waves rather than a cable infrastructure.
- the major motivation and benefit from WLANs is increased mobility. Untethered from conventional network connections, network users can move about almost without restriction and access LANs from nearly anywhere. Wireless LANs also offer the connectivity and the convenience of wired LANs without the need for expensive wiring or rewiring.
- the 5 GigaHertz (GHz) band is of particular interest for high bandwidth WLAN products. Being spectrally clean and wide, the 5 GHz band attracts much attention as being the enabler of wide public acceptance for broadband WLAN products. In the US, the 5 GHz .
- U-NII Unlicensed National Information Infrastructure
- the 200 mW band provides for in-building operation.
- the 1 W band allows campus or small neighborhood services.
- the 4W band allows for services of up to approximately 10 km.
- the 5 GHz band is open in Europe, the United States and Japan.
- the current spectrum allocation at 5 GHz comprises 455 MHz in Europe, 300 MHz in the US, and 100 MHz in Japan.
- Two WLAN standards (protocols) for the 5 GHz band have emerged, the IEEE
- 802.1 la hereinafter referred to as “802.11” or “11a”
- HiPerLAN/2 hereinafter referred to as "HL2”
- 802.11 802.11
- HL2 HiPerLAN/2
- Ethernet elements 11a elements may be referred to as Ethernet elements.
- Multimedia elements HL2 elements may be referred to as Multimedia elements.
- Co-existence The ability of two wireless elements, each consistent with a different protocol both at the same frequency, to work adjacently without interference.
- Partial Interoperability The ability of two wireless elements, each consistent with a different protocol, to exchange information through a third element.
- Mobile Terminal This term is used to describe all wireless network elements except the Access Point, including stationary terminals, in both the 11a and HL2 standard(s). With reference to the present invention, the following prefixes will be used.
- the IEEE 802.11 (“11a”) standard is a broadband communication standard for WLANs, and defines two pieces of equipment, a wireless station (STA, herein "MT"), which is usually a personal computer (PC) equipped with a wireless network interface card (NIC), and an access point (AP), which acts as a bridge between the wireless and wired networks.
- STA wireless station
- MT wireless station
- NIC wireless network interface card
- AP access point
- An AP usually consists of a radio, a wired network interface (e.g., Ethernet), and bridging software conforming to the IEEE 802. Id bridging standard.
- the AP acts as the base station for the wireless network, aggregating access for multiple MTs onto the wired network.
- Wireless stations can be 802.11 PC Card, PCI, or ISA NICs, or embedded solutions in non-PC clients (such as an 802.11 -based telephone handset).
- the 11a standard defines two modes of operation - an infrastructure mode and an ad-hoc mode.
- the wireless network consists of at least one AP connected to the wired network infrastructure and a set of MTs. This configuration is called a Basic Service Set (BSS).
- An Extended Service Set (ESS) is a set of two or more BSSs forming a single subnetwork. Since most corporate wireless LANs require access to the wired LAN for services (file servers, printers, Internet links) they typically operate in infrastructure mode.
- the ad-hoc mode (also called peer-to-peer mode, or Independent Basic Service Set, IBS) is simply a set of wireless stations (MTs) that communicate directly with one another without using an AP or any connection to a wired network.
- This mode is useful for quickly and easily setting up a wireless network anywhere that a wireless infrastructure does not exist or is not required for services, such as in a hotel room, convention center, or airport, or where access to the wired network is barred (such as for consultants at a client site).
- the 11a standard includes both a physical (PHY) layer and a medium access control (MAC) layer of the network.
- PHY physical
- MAC medium access control
- the PHY layer handles the transmission of data between nodes
- the MAC layer is a set of protocols which is responsible for maintaining order in the use of a shared medium.
- the 11a MAC layer is responsible for how a wireless station (MT) associates with an access point (AP).
- AP access point
- an MT When an MT enters the range of one or more APs, it chooses an AP to associate with (also called "joining the Basic Service Set"), based on signal strength and observed packet error rates.
- the MT tunes to the radio channel to which the AP is set.
- the MT surveys all of the available channels in order to assess whether a different AP would provide it with better performance characteristics. If it determines that this is the case, the MT reassociates with the new AP, tuning to the radio channel to which that AP is set. Reassociation usually occurs because the MT has physically moved away from the original AP, causing the signal to weaken.
- a MAC-layer problem specific to wireless LAN is the "hidden node” issue, in which two stations on opposite sides of an AP can both “hear” activity from the AP, but not from each other, usually due to distance or an obstruction.
- RTS/CTS Request to Send/Clear to Send
- a sending station transmits an RTS and waits for the access point to reply with a CTS. Since all stations in the BSS can hear the access point, the CTS causes them to delay any intended transmissions, allowing the sending station to transmit and receive a packet acknowledgment without any chance of collision.
- HL2 is a another wireless LAN standard which includes both a Physical (PHY) Layer and a Medium Access Control (MAC) layer, and other layers as described hereinbelow.
- HL2 provides high-speed communications with a bit rate of up to 54-Mbits/s between Mobile Terminals (MTs) and various broadband infrastructure networks.
- the HL2 standard relies on cellular networking topology combined with an ad-hoc networking capability. It supports two basic modes of operation: centralized mode and direct mode.
- the centralized mode is used in the cellular networking topology where each radio cell is controlled by an access point (AP) covering a certain geographical area. In this mode, a mobile terminal (MT) communicates with other mobile terminals (MTs) or with the core network via an AP.
- AP access point
- This mode of operation is mainly used in business applications, both indoors and outdoors, where an area much larger than a radio cell has to be covered.
- the direct mode is used in the ad-hoc networking topology, mainly in typical private home environments, where a radio cell covers the whole serving area.
- MTs mobile terminals
- network can directly exchange data.
- the PHY layer maps MAC Protocol Data Units (PDUs) to PHY PDUs, and adds PHY signaling such as system parameters and headers intended for RF signal synchronization.
- PDUs MAC Protocol Data Units
- PHY signaling such as system parameters and headers intended for RF signal synchronization.
- the signal modulation is based on Orthogonal Frequency Division Multiplexing (OFDM) with several sub-carrier modulation and forward error correction combinations that allow to cope with various channel configurations.
- OFDM Orthogonal Frequency Division Multiplexing
- An intermediate layer deals with channel access signaling and protocol operation required to support packet priority.
- a pseudo-hierarchically independent access mechanism is achieved via active signaling in a listen-before-talk access protocol. This mechanism (Elimination- Yield Non-Preemptive Multiple Access, EY-NPMA) codes priority level selection and contention resolution into a single, variable length radio pulse preceding packet data. EY-NPMA provides good residual collision rate performance for even large numbers of simultaneous channel contenders.
- the HL2 standard also includes a Data Link Control (DLC) layer.
- DLC Data Link Control
- Two specifications address the basic part of the DLC layer. The first one includes the basic data transport functions consisting of Error Control protocol and Medium Access Control (MAC) protocol.
- the second specification defines the Radio Link Control (RLC) Sublayer that is used for exchanging data in the control plane between an access point (AP) and a mobile terminal (MT).
- RLC Radio Link Control
- AP access point
- MT mobile terminal
- two specifications are developed for Home and Business profiles of the DLC.
- the air interface of HL2 is based on Time Division Duplex (TDD) and dynamic Time Division Multiplex (TDMA).
- TDD Time Division Duplex
- TDMA dynamic Time Division Multiplex
- the HL2 standard also specifies Convergence Layers (CLs).
- CLs Convergence Layers
- a CL has two main functions: Adapting service requests from higher layers to the services offered by the DLC and converting the higher layer packets with fixed or variable size into fixed-size DLC Service Data Units that is used within the DLC.
- Convergence layers have been developed for Ethernet (IP based) applications, cell based core networks as ATM and for IEEE 1394 protocols and applications.
- the HL2 standard defines a set of protocols (measurements and signaling) to provide support for a number of radio network functions, e.g. Dynamic Frequency Selection (DFS), link adaptation, handover, multi beam antennas and power control, where the algorithms are vendor specific.
- the supported radio network functions allow cellular deployment of HL2 systems with full coverage and high data rates in a wide range of environments.
- the system automatically allocates frequencies to each access point for communications. This is performed by the DFS, which allows several operators to share the available spectrum by avoiding the use of interfered frequencies. Performance is one of the most important factors when dealing with wireless LANs.
- QoS quality of service
- the HL2 standard uses a link adaptation (LA) scheme, the aim of which is keeping up communications link at low signal-to-interference ratios in order to maintain the QoS, and to trade off between communications range and data rate.
- LA link adaptation
- the physical layer data rate is adapted to the current link quality.
- Transmitter power control is supported in both mobile terminal (uplink) and access point (downlink).
- the uplink power control is mainly used to simplify the design of the access point receiver by avoiding automatic gain control at access point.
- the main goal of downlink power control is to fulfill the regulatory requirements in Europe to decrease interference to other systems using the same 5 GHz band.
- a typical HL2 MAC Frame is of 2 ms duration, and comprises the following functions/phases:
- both of the 11a and HL2 standards have chosen the same OFDM-based approach in the PHY layer. Therefore, harmonization of the PHY layer is relatively straightforward, and needs no further discussion.
- the 11a and HL2 standards have implemented very different solutions in the MAC layer. While the 11a standard CSMA/CA MAC is optimized for wireless data communication, providing simple and field proven solution for wireless Ethernet and IP, the HL2 standard, with its build-in support for quality of service (QoS), provides robust solution for wireless multimedia transmission.
- QoS quality of service
- HL2 is basically centrally controlled, with the AP/CC announcing the time structure at the beginning of each MAC frame. This is in marked contrast to CSMA CA of the 11a standard, which is essentially a simple Listen-Before-Talk scheme. HL2 allows the dynamic allocating of new frequencies (Dynamic Frequency
- LA Adaptation
- Mangold describes a simulated scenario wherein an 802.11 AP communicates with two MTs which are each at a distance of a few meters from the 802.11 AP, and a nearby HL2 AP communicates with two MTs which are also each at a distance of a few meters from the AP, and both systems are transmitting their packets at the same frequency using the same carrier.
- 802.11 AP communicates with two MTs which are each at a distance of a few meters from the 802.11 AP
- a nearby HL2 AP communicates with two MTs which are also each at a distance of a few meters from the AP, and both systems are transmitting their packets at the same frequency using the same carrier.
- the 802.11 packets sent after carrier sensing and after Ready To Send (RTS) and Clear To Send (CTS) bursts very often interfere with the BCH PDU of HL2 at the beginning of the MAC frame.
- RTS Ready To Send
- CTS Clear To Send
- the AP will transmit negative acknowledgement (NAK) at the slot as soon as it has detected an unused random access slot. This could be performed by transmitting energy bursts after detecting that no access happened. No idle periods longer than the inter frame space necessary for starting a transmission of 802.11 occur, and the 802.11 systems do not interfere in times when HL2 is required to guarantee QoS for real-time traffic such as voice or multimedia.
- NAK negative acknowledgement
- Mangold proposes a transmission suppression mechanism, wherein the transmission of 802.11 frames will be suppressed by HL2, so that it will never have the chance to be used when operated in HL2 environment. Therefore, this is not a co-existence solution, it is merely an approach to interference avoidance (HL2 can be operated but 802.11 can not).
- MMAC Multimedia Mobile Access Communications
- Ethernet A LAN protocol See IEEE 802.2
- H2 HIPERLAN High Performance Radio Local Area Network
- PCF Point Coordination Function PCI Peripheral Component Interconnect
- WLANs which provides for the fair co-existence of the 11a and HL2 broadband communications standards.
- WLANs which provides for the fair co-existence of the 11a and HL2 broadband communications standards.
- These two incompatible standards are planned to operate on the same frequency bands, leading to incompatible products and impossible interoperability between the two environments.
- multiple standards, product incompatibilities and poor interoperability impose a major hurdle for wide public acceptance.
- the present invention provides such a unified communications protocol which ensures that these two standards may fairly co-exist, without being able to communicate with one another and without exchanging resource requests or grants, and which allows each system the opportunity to protect their active terminal (MT) during communication phases and to guarantee a certain Quality of Service (QoS).
- MT active terminal
- QoS Quality of Service
- a technique for combining the 11a and HL2 standards, enabling protocol co-existence, and improved interoperability between these two WLAN standards, thereby providing a globally-harmonized, synergistic 5 GHz Wireless LAN solution.
- the principle is generally to combine the best from the two standards, while maintaining one coherent, and relatively simple solution.
- the ultimate object of the present invention is providing a unified standard which fulfills the following conditions: - Achieving all-around interoperability, wherein the same device is able to connect, be serviced and to serve in any of the home, office and public environment.
- the products co-exist and share infrastructure and resources.
- Wireless LAN applications require various advanced features, including the ability to deliver wide variety of protocols (e.g., Ethernet, IP, IEEE 1394, and others), quality of service (QoS) support, and robust privacy support (encryption, authentication). Regulations in many countries require radio link functionality for dynamic frequency selection and transmission power control. All those features are integrated into the unified standard of the present invention, without overloading the system with umiecessary complexities, keeping the standard as simple to use and implement as possible.
- protocols e.g., Ethernet, IP, IEEE 1394, and others
- QoS quality of service
- Encryption, authentication encryption, authentication
- the present invention can be implemented in a stepwise manner that is suitable to be introduced in phases, each of which may be considered to be an embodiment of the invention, as follows:
- Phase 1 This phase enables Co-existence and partial interoperability of both the
- Phase 1.1 This sub-phase is based on the original APs (E-AP & M-AP) with a partial arbitrator entity (ARB) added to one of the APs.
- Phase 1.2 This sub-phase is based on one U-AP.
- Phase 2 This phase enables co-existence and full interoperability of both the
- the PHY layer is 1 la
- the MAC layer is essentially a simplified version of HL2 superimposed upon the basic 11a MAC. This results in: High QoS Full Co-existence Partial Interoperability
- the PHY layer is 11a
- the MAC layer is a hybrid (combination) of HL2 and 11a. This results in: High QoS Full Co-existence Full Interoperability
- the first phase (or “intermediate solution"), co-existence is achieved between the two standards by dynamically dividing the time domain of each subnetwork at its Access Point (AP), between the 11a and the HL2 devices.
- the time division between these different devices is performed by an Arbitrator (ARB) entity.
- ARB Arbitrator
- This phase is considered to be "partial” because the ARB only controls the time slices.
- This can be implemented in the wireless network with either: two separate APs, one for each environment, each including the ARB entity; or: one integrated AP servicing both environments, and including the ARB entity.
- connections which may be wire-line connections, between the 1 la (Ethernet-like) AP and the HL2 (Multimedia) AP. These APs will handle the bridging between the environments.
- U-AP unified AP
- MTs wireless terminals
- E-MTs which are simple Ethernet-like devices which support only Ethernet environments.
- U-MTs which are hybrid devices that support both Multimedia and Ethernet. Since U-MTs can talk to E-MTs, full interoperability is achieved.
- a method of enabling wireless network devices (MTs), operating in accordance with two incompatible communications standards, to co-exist without interference comprises partitioning a periodic time domain into a first slice for use by devices (E-MTs) operating in accordance with a first communications standard, and a second slice for use by devices (M-MTs) operating in accordance with a second communications standard, and broadcasting the time slices to the MTs.
- the first communications standard consists essentially of the IEEE 802.11a ("11a") standard
- the second communications standard consists essentially of the HiPerLAN/2 (“HL2”) standard.
- an Arbitrator entity broadcasts the time slices, either once every periodic time domain, or periodically at an interval which is greater than the period of the periodic time domain. (The ARB message is transmitted fewer than once every period.)
- guard periods are introduced between the two slices to prevent overlapped operation of E-MTs and M-MTs.
- These time slices may be substantially equally partitioned, or may be unequally allocated based on activity of the wireless network devices (MTs).
- E-MTs are prevented from transmitting outside of the first time slice. This may be accomplished by setting all other time slices in the time domain as busy in a network allocation vector (NAV) of the first communications standard.
- NAV network allocation vector
- data frames being sent by an E-MT which are larger than its allocated time slice may be fragmented for transmission during a plurality of time slices.
- a small fragment size may be forced on the data frames of the E-MTs; and a guard time (contention-free period) may be provided before the second time slice, wherein the guard time is sufficient for the E-MT to send one small sized fragment.
- a first Access Point (E-AP) is provided for handling communications with the E-MTs in an Ethernet environment, and a second Access
- M-AP Mobile Multimedia Subsystem
- a unified Access Point (U-AP) is provided for communicating with the E-MTs and the M-MTs in a multiple (Ethernet plus multimedia) environment, thereby providing a full solution.
- U-AP unified Access Point
- Figure 1 is timing diagram of an embodiment of a unified protocol combining the 11a and HL2 standards, with partial interoperability, according to the invention
- Figure 2 is timing diagram of an alternate embodiment of a unified protocol combining the 1 la and HL2 standards, with full interoperability, according to the invention
- Figure 3 is a graphic illustration of a 2ms time frame divided into 2 equal parts, one
- H2 Mgmt H2 Management
- Figure 4 is a graphic illustration of a wireless communications network implementing a "partial" solution, wherein some of the MTs operate in the Multimedia environment and other of the MTs operate in the Ethernet environment, according to the invention.
- FIG. 5 is a graphic illustration of a wireless communications network implementing a "full” solution, wherein all of the MTs are Universal MTs (U-MTs) operating in a Multiple (Multimedia plus Ethernet) environment, according to the invention.
- U-MTs Universal MTs
- FIG. 5 is a graphic illustration of a wireless communications network implementing a "full” solution, wherein all of the MTs are Universal MTs (U-MTs) operating in a Multiple (Multimedia plus Ethernet) environment, according to the invention.
- the same wireless network can be shared by data communication centric devices using the 1 la protocol and by multimedia centric devices using the HL2 protocol for QoS support.
- the ultimate objective of the unified protocol of the present invention is gaining full interoperability between the different operational environments, features of the individual 11a and HL2 standards are eliminated which may jeopardize full interoperability.
- the 11a standard is pretty much "self interoperable" - in other words, there are no "operation environments” or special considerations regarding the ability to operate any 11a device in an ad-hoc or infrastructure network.
- the HL2 standard introduced the concept of different operation environments (or profiles), optimizing the ability of specific devices to operate in the home, business (office) or public environments, using different operation extensions.
- HL2 may be used as part of a corporate network dominated by Ethernet traffic, and is used as a wireless Ethernet.
- HL2 may be used for home networking, and both data and multimedia (audio and video) applications are using the channel - for example, internet connection and cordless phones both using HL2 as the transport layer - and a high degree of Quality of service is very important in these environment.
- HL2 may be used in airports, shopping centers and hotels where the applications are both data networking (as in the business profile) but can also be UMTS and other multimedia traffic. Billing, access control and security have high importance in the public profile.
- This partitioning to different environments provides some optimization for devices targeted for specific applications, but only at the expense of interoperability. Therefore, as an initial step towards achieving full interoperability of devices, the present invention consolidates the three different HL2 operation profiles, into one "unified" profile, preferably based on the "home” extension of the operational environment.
- This unified profile support the necessary QoS, IEEE 1394 and ad-hoc networking features, with business Ethernet support provided by the 11a co-existent features, thereby eliminating the need to incorporate the business profile extensions.
- the use of a single all-around operation profile ensures high degree of interoperability.
- a simplified version of HL2 is overlaid onto the basic 11a MAC, and the resulting time domain is divided (partitioned, allocated) between 11a and HL2 devices.
- the "first" slice of the time is used as dictated by the respective standard, while the "second" slice of the time is forbidden to use by that standard.
- the partitioning of the time between the protocols is exclusive.
- An "arbitrator” (ARB) entity manages and broadcasts the time slices provided for each of the protocols, dividing the time domain between the 1 la and HL2 slices.
- the ARB entity may be either of the 1 la or HL2 access points (APs), a separate central controller (CC), or any one of the wireless stations (MTs) in the network.
- the 11a devices are capable of interpreting the broadcast delivered by the arbitrator (ARB), such that no 11a device transmits outside the allocated 11a time slice. These periods are dealt with like contention-free periods. Within the 11a time slice, the normal 11a protocol may be used, and both DCF and PCF modes may be incorporated. Guard periods may be introduced to guard between the 1 la and HL2 time domains, in order to prevent overlapped operation of HL2 and 11a devices, caused by synchronization faults.
- the HL2 central controller (TDMA manager, "CC") is capable of interpreting the broadcast message delivered by the ARB, and to allocate HL2 frames such that no HL2 device is allowed to transmit outside the allocated HL2 time slice.
- TDMA manager TCMA manager
- different sorts of dynamic allocation and policy-based solutions may optionally be incorporated by the ARB entity to enable allocating sufficient resources for QoS-bound traffic while leaving additional bandwidth for data communication traffic. Incorporating policy, based on traffic management solution, will allow limiting both data communication and multimedia traffic usage by user configuration.
- the unified protocol of the present invention does not impose any significant bandwidth degradation compared to current bandwidth capabilities available in either of the 1 la or HL2 standards.
- the HL2 protocol relies heavily on two-millisecond periodic frame generation.
- the 1 la protocol does not impose any specific periodicity restrictions, as long as the 11a slices are scheduled in close enough time periods avoiding the generation of higher layer protocol retransmissions, due to timeouts. Since retransmission timeout considerations must be accounted for, the unified protocol of the present invention utilizes the 2-millisecond periodic clocking scheme of the HL2 standard.
- Figure 1 and Figure 2 illustrate an embodiment of a unified protocol frame structure of the present invention, from the 11a viewpoint and from the HL2 viewpoint, respectively. It should be understood that the frame layout is only an exemplary one of many possible embodiments which can be implemented.
- Figure 1 illustrates the scheduling layout (frame structure) of a unified protocol 100 combining the 11a and HL2 standards, with partial interoperability, from the 11a viewpoint, according to the invention.
- An overall periodic frame having a duration of approximately 2 ms, is divided into two slices, an 1 la slice 102 followed by an HL2 slice 104.
- a number of functions are performed during the periodic frame, as follows (and as tabulated hereinbelow, in Table 1):
- a first portion 106 of the 11a slice 102 is dedicated to the DCF and PCF functions, and has a duration of approximately 1.10 ms.
- a second portion 108 of the 11a slice 102 is dedicated to the ARB function, and has a duration of approximately 0.06 ms.
- a first portion 110 of the HL2 slice 104 is dedicated to the RCH function, and has a duration of approximately 0.06 ms.
- a second portion 112 of the HL2 slice 104 is dedicated to the BCH function, and has a duration of approximately 0.06 ms.
- a third portion 114 of the HL2 slice 104 is dedicated to the FCH function, and has a duration of approximately 0.06 ms.
- a fourth portion 116 of the HL2 slice 104 is dedicated to the ACH function, and has a duration of approximately 0.06 ms.
- a fifth portion 118 of the HL2 slice 104 is dedicated to the DL function, and has a duration of approximately 0.12 ms.
- a sixth portion 120 of the HL2 slice 104 is dedicated to the DIL function, and has a duration of approximately 0.32 ms.
- a seventh portion 122 of the HL2 slice 104 is dedicated to the UL function, and has a duration of approximately 0.16 ms.
- the 11a time slice 102 comprises a "regular" DCF/PCF period 106 followed by a special ARB broadcast message 108 announcing the start point and length of the following DCF/PCF period.
- the 11a stations are not allowed transmission outside the DCF/PCF periods, inside those periods the regular 1 la rules fully apply.
- the HL2 protocol is using the allocated bandwidth as broadcasted in the FCH message; the HL2 CC must not schedule HL2 traffic outside the HL2 slice.
- the presented example is best suited for cases in which the 11a access point (AP) is used as the HL2 central controller (CC) entity and the arbitrator (ARB), as close synchronization is required between the ARB and the CC entities.
- AP access point
- CC central controller
- ARB arbitrator
- Figure 2 illustrates the scheduling layout (frame structure) of the unified protocol 200 combining the 1 la and HL2 standards, with partial interoperability, from the HL2 viewpoint, according to the invention.
- An overall periodic frame having a duration of approximately 2 ms, is divided into two slices, an HL2 slice 202 followed by an 1 la slice 204.
- a number of functions are performed during the periodic frame, as follows (and as tabulated hereinbelow, in Table 2).
- a first portion 206 of the HL2 slice 204 is dedicated to the BCH function, and has a duration of approximately 0.06 ms.
- a second portion 208 of the HL2 slice 204 is dedicated to the FCH function, and has a duration of approximately 0.06 ms.
- HL2 slice 204 is dedicated to the ACH function, and has a duration of approximately 0.06 ms.
- the RCH function is located at the end of the 11a slice. However, this being a periodic frame, the end of the 11a slice is essentially comparable to the beginning of the next HL2 slice.
- a fifth portion 212 of the HL2 slice 204 is dedicated to the DL function, and has a duration of approximately 0.12 ms.
- a sixth portion 214 of the HL2 slice 204 is dedicated to the DIL function, and has a duration of approximately 0.32 ms.
- HL2 slice 204 is dedicated to the UL function, and has a duration of approximately 0.16 ms.
- the order of the DL, DIL and UL functions is the same as for the protocol of Figure 1.
- the DIL function is shown as having been lengthened (prolonged). In striving to make the unified profile resemble as much as possible the "home" profile, which makes extensive use of DIL, the DIL may be prolonged.
- a first portion 218 of the 11a slice 204 is dedicated to the DCF and PCF functions, and has a duration of approximately 1.10 ms.
- a second portion 220 of the 11a slice 204 is dedicated to the ARB function, and has a duration of approximately 0.06 ms.
- the order of the DCF/PCF and ARB functions is the same as for the protocol of Figure 1.
- the unified protocol of the present invention incurs a "cost", per se, by adding "management" information which is transmitted by the ARB entity in order to synchronize the 1 la and HL2 time slices.
- the impact is surprisingly minimal.
- a frame created is as shown in Figure 3.
- a third portion (or slice) of the frame is allocated to management (H2 Mgmt, ARB broadcast).
- FIG. 4 illustrates an embodiment of a wireless communications network 400 implementing a "partial" solution, such as has been discussed hereinabove.
- a first portion of the MTs operate in the Multimedia (HL2) environment and are labeled "M-MT", a second portion of the MTs operate in the Ethernet (1 la) environment and are labeled "E-MT".
- a Multimedia AP communicates with the M-MT's.
- An Ethernet AP communicates with the E-MTs.
- the M-MTs can communicate with one another.
- the E-MTs can communicate with one another.
- the M-MTs cannot communicate directly with E-MTs, and vice- versa.
- An Access Point (AP) is provided in each of the Multimedia (HL2) and Ethernet (11a) environments.
- An arbitrator function (ARB) is provided in the Multimedia AAP for managing interactions.
- the wireless network includes two separate APs, one for each environment (Multimedia and Ethernet).
- the two separate APs, an Ethernet AP (E-AP) and a Multimedia AP (M-AP) communicate with one another via a communications link, such as via land-lines or over an air channel, functioning as a bridge between the two APs.
- the ARB is illustrated as being implemented in the M-AP, and it is "partial" because it doesn't include the full AP mission, but only exercises control over the time slices. It is within the scope of the invention that the ARB could be implemented in the E-AP. It is within the scope of the invention that the ARB can include the missions of both environments.
- Figure 5 illustrates an embodiment of wireless communications network 500 implementing a "full" solution, such as has been discussed hereinabove, in a Multiple (Multimedia plus Ethernet) environment.
- the Multiple Environment is also referred to as a "Harmonized Network".
- U-AP unified AP
- E-MT E-MT
- M-MT M-MTs.
- the U-MTs can communicate with one another.
- the E-MTs can communicate with one another, but not with U-MTs.
- the ARB is shown as being implemented in the U-MT.
- the Arbitrator (ARB) entity is responsible for partitioning the time domain between protocols. It can be combined with the E-AP or with the M-AP. It can be selected dynamically (as in dynamic HL2 CC election). The protocol partitioning may be policy based and dynamic to ensure maximal efficiency. The 11a and HL2 devices must transmit only inside their allocated time slices.
- the ARB is required to be present on the harmonized network at all times. Its task is to partition the time domain between the 11a and HL2 protocols. The partitioning is performed by applying policy-based algorithms, and/or protocol utilization measurements for both 11a and HL2 sub-networks.
- the arbitrator entity generates the ARB broadcast message, instructing 11a and potentially the HL2 central controller (CC) for available time slices for the respective protocols.
- CC central controller
- the ARB's complexity is dependant on the employed scheduling algorithm and arbitrator management scheme.
- the management scheme is discussed hereinbelow.
- the scheduling algorithm its complexity may vary in accordance to applicable requirements.
- a static arbitrator is relatively straightforward to implement.
- a dynamic arbitrator would be a bit more complex. Perfecting the algorithm beyond a reasonable level is not desirable because it would produce a highly complex algorithm, which would only be marginally superior.
- the information that a typical ARB may use is the number of stations (MTs) in the network, traffic utilization and number of resource requests denied by the HL2 CC. Using these parameters and a set of configurable rules (via SNMP or other management protocol) the arbitrator (ARB) can update the resource allocation demands.
- the management functions of the arbitrator entity bear some resemblance to the work done in BRAN considering central controller (CC) behavior in the HL2 ad-hoc network scenario, namely procedures for CC election, handover between CCs and other related issues.
- CC central controller
- the inclusion of ARB message in each 2-millisecond period might be considered as unnecessary.
- it is preferred that the ARB message is transmitted once every longer time periods (each 500 milliseconds for example), and that arbitrator will allocate a minimal time slice for the other protocol, to allow the association of devices using that protocol.
- the time period will include the probe message, and a delay to allow authentication and associations request generation by STAs (MTs).
- the time period will include the generation of a BCH, minimal FCH (no allocation of traffic), minimal ACH and the RCH to allow association of mobile terminals.
- the arbitrator shall increase the time slices allocated for that protocol. This scheme will optimize traffic utilization of monolithic networks, in the cost of prolonging the association process.
- the arbitrator entity does not need to support both the 1 la and HL2 standards. Therefore, it is possible to implement a simple protocol by which both the HL2 CC and one of the 11a STAs (E-MT) are reporting to the arbitrator (ARB).
- the 1 la AP E-AP
- the ARB will have a good picture of traffic utilization and requirements for the different protocols, and there is no need for having a specific reporting protocol.
- Another added value from such a configuration is the ability to gain interoperability between the 11a and HL2 devices through the use of the AP as a relay.
- Interoperability between the various operational environments is achieved by using the same unified protocol on all environments. This ensures co-existence of devices intended for the different operational scenarios, so that both can work and share the same band.
- an optional network entity that is able to recognize both protocols. In the typical case it will be the 1 la/HL2 access point/central controller (AP/CC). This entity would provide protocol translation facilities to enable data transfer between HL2 and 11a devices.
- office data-communication centric devices will use the 11a protocol
- home multimedia centric devices will use the HL2 protocol.
- partitioning described hereinabove covers the main part of these devices activities, it is important to allow data communication devices some degree of QoS support, and to allow multimedia devices the ability to use asynchronous communications for control and other purposes.
- One solution is to require each device to support both protocols.
- Light QoS provides most business requirements for QoS, as it delivers the ability to support their wired equivalents. These will enable business devices to maintain the simplicity and remain 11a based.
- HL2 currently business and home extension profiles are introduced
- 11a standard provides robust and simple solution for business devices, it is preferred to simply eliminate the business and public profiles, and establish the single HL2 profile used in the unified protocol on the basis of the "HL2 home extensions".
- the home extensions to the HL2 protocol deliver QoS, IEEE 1394 and ad-hoc networking supported all are major prerequisites for the unified protocol of the present invention.
- signaling and non-QoS traffic concepts are already integrated into the HL2 protocol, enabling them for multimedia devices inside HL2 is a non-issue.
- the maximal 11a MAC frame size may be larger than the allocated 2 millisecond time slice. Therefore, according to the invention, the transmission of arbitrary 11a frames is enabled by applying fragmentation.
- the maximum frame fragment size will be determined by the size of the 11a transmission time slice and the transmission data rate.
- the minimal slice size value can be specified and distributed around the BSS (During the ARB broadcast for example), and it is guaranteed that any allocated 11a time slice shall not be shorter then this value.
- the fragment size shall be calculated using the minimal slice size. In typical situations (e.g., 16 QAM), a 600-microsecond slice for the 1 la protocol can suffice for un-fragmented transmission of a maximal length Ethernet packet. Typically, fragmentation will be avoided. Fragmentation of multicast and broadcast frames is not normally supported within the
- the 1 la MAC is enhanced to support fragmentation of broadcast and multicast messages.
- no acknowledgment is sent, and no retransmission of fragments is supported.
- This is coherent with un-fragmented multicast and broadcast traffic specifications in 802.11, in which no acknowledgment is supported.
- E-MTs 11a MTs
- HL2 time slice will be preceded by a guard time that will be enough for an E-MT to send one fragment.
- - fragment size is approximately 100 microseconds
- - guard time is approximately 100 microseconds.
- the HL2 transmissions will be safe from interference by 11a transmissions that began shortly before the HL2 time slice. Because of this, there will be a contention free period of up to one fragment transmission time, before the HL2 time slice.
- This frame size should be small enough not to cause channel efficiency to drop. This feature is only relevant to environments accommodating "old" 11a MTs, to ensure backward compatibility. In an environment without older 11a MTs, it can be disabled, or simply ignored. Preventing an E-MT from transmitting outside of the 11a time slice
- a specific 11a station STA starts its transmission (after carrier sensing or CTS in DCF mode, or after being polled by the PC in PCF mode) it will not consider any external timing constrains, and the complete frame (or fragment) will be sent. In order to implement the universal protocol of the present invention, it is therefore necessary ensure that there is no E-MT (STA) transmitting outside the 1 la time slice.
- the existing l la-MAC functionality supports virtual carrier-sense mechanisms through the concept of NAV (network allocation vector) to predict future traffic on the medium according to duration indications in various frames (RTS/CTS, CP, etc.).
- time slices not allocated to the 11a protocol will be set as busy by the lla-NAV.
- Each ARB broadcast will update the NAV with the duration of the next HL2 slice and ARB broadcast message, indicating it as "busy".
- all 1 la devices will therefore be limited to using only the 11a allocated slices.
- the notion of "look-ahead NAV" implies that each transmitting STA (MT) must check that the frame size fits inside the allowed slot, and does not collide with a look ahead NAV. If the frame size does not fit into the slot, the STA will suspend the transmission of the frame until the next available slot.
- Reasonable clock synchronization between the STAs in the BSS can be maintained in order for this mechanism to work, and may be achieved by the beacon and clock synchronization mechanisms available in the 1 la-MAC.
- Modifications to the HL2 protocol, to allow protocol co-existence include changes to the associations process. As it is not promised that each 2 millisecond period a BCCH message will be generated, each device should be able to wait for longer periods on each frequency band.
- the HL2 central controller (CC) must be synchronized with the arbitrator (ARB), so that time-slice allocations do not collide, the CC scheduling algorithm must be aware of the "occupied" TDMA slots not allocating them to any HL2 device.
- Modifications to the 11 a protocol, to allow protocol co-existence include
- the invention is beneficial in that it combines and enables co-existence between IEEE 802.11a (11a) and HIPERLAN/2 (HL2) protocols. Having one global interoperable 5GHz standard (universal protocol) will greatly simplif the worldwide adoption of Wireless LAN technology. By using the strongest features of both 11a and HL2, dedicated devices for the various operation environments may share the same network and exchange data, with no major effects on device complexities.
- the invention provides a feasible framework, generally, for the universal protocol.
- Wireless business devices are based on the field proven and existing 11a standard, ensuring rapid development and low cost.
- Wireless multimedia is enabled through the clean and robust HL2 standard. No patches and minimal adaptations and modifications are proposed to enable wireless multimedia, and the co-existence between data communication and multimedia.
- Another degree of simplicity is achieved by applying a single profile solution for all devices. This ensures that users will not be required to manage separate wireless solutions and to deal with any incompatibility issues. As same wireless network protocols are enabled all over the world, users are not required to maintain several hardware devices or several configurations.
- the HL2 standard is full of options, which makes the protocol very adaptive and robust, but increases implementation complexities. Care must be exercised when different vendors implement different options.
- the lowest common denominator approach should preferably be used, which is not desirable for QoS support, error control or privacy, etc.
- the lowest common feature may be lack of QoS, lack of Error control, etc. It is important to minimize the available protocol options, to set the required options as mandatory, and to eliminate as much "optional" directive as possible. This can be applied for QoS support (use FSA-fixed a lot allocation method, eliminate FCA-fixed capacity agreement method), error control (set RS and ARQ, eliminate repetition), Privacy (limit the number of possible options for key management and authentication).
Abstract
Description
Claims
Priority Applications (3)
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AU2002229157A AU2002229157A1 (en) | 2000-08-09 | 2001-07-11 | Communications protocal for wireless lan harmonizing the ieee 802.11a and etsi hiperlan/2 standards |
EP01984507A EP1320952A1 (en) | 2000-08-09 | 2001-07-11 | COMMUNICATIONS PROTOCOL FOR WIRELESS LAN HARMONIZING THE IEEE 802.11a AND ETSI HiPerLAN/2 STANDARDS |
US10/344,163 US20040141522A1 (en) | 2001-07-11 | 2001-07-11 | Communications protocol for wireless lan harmonizing the ieee 802.11a and etsi hiperla/2 standards |
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US22399300P | 2000-08-09 | 2000-08-09 | |
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AU (1) | AU2002229157A1 (en) |
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AU2002229157A1 (en) | 2002-02-18 |
TW548935B (en) | 2003-08-21 |
EP1320952A1 (en) | 2003-06-25 |
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