Wireless Wonders Coming Your Way
`
`Published May 2000, Network Magazine.
`
`HiperLAN2 wireless LANs and the Bluetooth specification promise to revolutionize
`connectivity. By Peter Rysavy.
`
`Wireless LAN technology is about to undergo dramatic advances, and the number and types of
`applications that wireless LANs will enable will sprout like weeds. Two technologies pushing the
`rapid evolution of this market are High Performance Radio LAN (HiperLAN) and Bluetooth
`(named after a 10th century Danish king).
`HiperLAN, which comes in several flavors, is a next-generation, high-speed wireless LAN
`technology that offers end users throughputs as high as 25Mbits/sec. This article will focus on
`one particular version: HiperLAN2. Bluetooth is more of a personal productivity wireless
`technology, with a range of about 10 meters. It is designed to eliminate all those pesky cables
`that hamper the use of high-tech gadgetry. Both technologies are huge innovations in applying
`state-of-the-art methods to practical ends.
`
`A lot has happened recently in the local wireless market, so this article will briefly survey these
`developments. Also, because HiperLAN and Bluetooth are not the only games in town, this
`article will stack them up against some of the competing technologies before examining them
`on their own merits.
`LANSCAPE
`
`A number of forces are driving the wireless LAN market. One force is product pricing, which has
`plummeted to as low as $200 per adapter for office products and half of that for home
`versions. For example, Apple’s IEEE 802.11b card lists for $99. Such low prices make wireless
`LANs a more cost-effective proposition.
`Standards, whether official or from industry consortiums, are also driving the market, as is the
`fact that the PC Card form factor is now common. In addition, large networking companies like
`Cisco Systems, Nortel Networks, Nokia, and Ericsson are all in the game, most through recent
`acquisitions.
`
` In addition, home use for sharing peripherals and broadband Internet connections is shaping
`up to be the killer application. Increasing numbers of users are standardizing on laptops as their
`only computer, making mobile connectivity highly desirable. The market doesn’t stop there,
`however: Hundreds of millions of cell phones are about to become Internet-enabled, and users
`will want to link up to laptops, headsets, hands-free kits in cars, and LAN access points.
`
`Exhibit 1036
`Apple, et al. v. Uniloc
`IPR2019-00251
`
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`

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`Clearly a need exists for low-cost, high-speed, local-area wireless connections, and numerous
`technologies are becoming available for these connections. The wireless LAN space has a
`variety of proprietary approaches, industry consortium standards (including OpenAir and
`HomeRF), IEEE 802.11 standards, and HiperLAN standards. The table contrasts the major
`technologies.
`HIPERLAN2
`
`HiperLAN2 represents the most sophisticated wireless LAN technology so far defined. It also has
`strong industry backing. Will it be the only standard deployed in that class? Probably not, as
`HiperLAN1 products will precede HiperLAN2, and IEEE 802.11a products will offer comparable
`performance. In fact, IEEE 802.11a and HiperLAN2 have the same Physical layer, so they can
`share the same components and reduce costs.
`The European Telecommunications Standards Institute (ETSI) is developing HiperLAN standards
`as part of an effort called Broadband Radio Access Network (BRAN). This effort includes four
`standards: HiperLAN1; HiperLAN2; HiperLink, designed for indoor radio backbones; and
`HiperAccess, designed for fixed outdoor use to provide access to a wired infrastructure.
`
` The HiperLAN1 standard is complete, and leading Wireless LAN vendor Proxim
`(www.proxim.com) is now delivering products based on it. HiperLAN1 offers the fastest route
`to market for a high-speed wireless LAN technology while minimizing the complexity of the
`radio technology.
`
` HiperLAN1 uses Gaussian Minimum Shift Keying (GMSK) modulation, which is well understood
`and broadly used in Global System for Mobile Communications (GSM) cellular networks and
`CDPD. In contrast, HiperLAN2 uses a new type of radio technology called Orthogonal Frequency
`Division Multiplexing (OFDM), which imposes significant technical challenges.
`
` Spectrum plays a crucial role in the deployment of next-generation wireless LANs. Currently,
`most local area wireless products operate in the unlicensed 2.4GHz band, which has several
`limitations: The band is only 80MHz wide, it mandates the use of spread spectrum technology,
`and wireless LAN users must not interfere with primary license holders.
`
` Recognizing the limitations of the 2.4GHz spectrum, licensing authorities around the world
`have allocated large blocks of spectrum in the 5GHz band. In the United States, 300MHz is
`available from 5.15GHz to 5.35GHz and 5.725GHz to 5.825GHz. In Europe, 300MHz is available
`from 5.15GHz to 5.35GHz and from 5.470GHz to 5.725GHz. Japan is considering a similar
`allocation.
`
` These broad blocks, combined with more lenient rules of operation, enable high-speed
`operation by large numbers of users. Both HiperLAN standards enjoy one key advantage over
`IEEE 802.11a in that they are approved standards for the European spectrum. IEEE 802.11a
`products may not be usable in Europe.
`
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`HiperLAN2 is being promoted by an industry group called the HiperLAN2 Global Forum
`(www.hiperlan2.com), which features such heavyweights as Bosch, Dell Computer, Ericsson,
`Nokia, Telia, TI, and Xircom. The HiperLAN2 standard will be completed in 2000, but the first
`HiperLAN2 products will not appear until 2001 and will not be widely available until 2002.
`
` The most compelling feature of HiperLAN2 is its high speed, which is sometimes misleadingly
`quoted at 54Mbits/sec. The raw over-the-air rate is indeed 54Mbits/sec, but sustained
`throughput for applications is closer to 20Mbits/sec. Another key feature is support for QoS,
`which will be important for applications like video and voice.
`
` The HiperLAN2 architecture provides for connections to multiple types of network
`infrastructures, including Ethernet (which will be the first one supported), IP, ATM, and PPP.
`Security features include authentication and encryption. An especially innovative feature is
`automatic frequency management, which significantly simplifies deployment. Each of these
`features is examined in the next section of this article.
`
` With its combination of high speed and QoS, HiperLAN will open up entire new classes of
`applications, such as video signal distribution into homes.
`UP THE STACK
`
`Like other wireless LAN technologies, HiperLAN2 lets mobile terminals connect to access points
`that bridge traffic to wired networks. It is also possible for mobile nodes to communicate
`directly with each other, though in practical deployments this will likely be the exception.
` HiperLAN2 works as a seamless extension of other networks, so wired network nodes see
`HiperLAN2 nodes as other network nodes. All common networking protocols at layer 3 (IP, IPX,
`and AppleTalk, for example) will operate over HiperLAN2, permitting all common network-
`based applications to operate.
`
` As Figure 1 shows, HiperLAN2 defines a Physical layer and a Data-link layer. Above these is a
`Convergence layer that accepts packets or cells from existing networking systems and formats
`them for delivery over the wireless medium.
`
` The first unique aspect of HiperLAN2 is OFDM. Though OFDM has been used before—in the
`European Digital Audio Broadcast (DAB) standard and in Asymmetric Digital Subscriber Lines
`(ADSLs)—it has never before appeared in a wireless LAN standard.
`
` OFDM is extremely effective in a time-dispersive environment where signals can take many
`paths to reach their destinations, resulting in variable time delays. At high data rates, these
`time delays can reach a significant proportion of the transmitted symbol (a modulated
`waveform), resulting in one symbol interfering with the next in what is called “intersymbol
`interference.”
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` OFDM combats this by dividing a radio channel into multiple subcarriers and transmitting data
`in parallel on them (see Figure 2). The aggregate throughput ends up being the same, but the
`data rate of each subcarrier is much lower, making each symbol longer—thus practically
`eliminating the effect of the variable time delays. However, OFDM demands extremely linear
`power amplifiers, which increase the cost of the radio. Consequently, HiperLAN2 products will
`likely cost more than lower-speed alternatives.
`
`In the spectrum allocation for Europe, HiperLAN2 channels will be spaced 20MHz apart—for a
`total of 19 channels. Each channel will be divided into 52 subcarriers, with 48 for data and four
`as pilots that provide synchronization. Synchronization enables coherent (in-phase)
`demodulation. Through digital signal processing, subchannels are divided through
`mathematical processing, rather than in the analog domain.
`
` OFDM by itself does not fully describe the Physical layer. There is also the question of how data
`is encoded and the type of modulation used in each subchannel. Encoding involves the serial
`sequencing of data, as well as Forward Error Correction (FEC). Most lower-speed wireless LANs
`do not employ FEC, but HiperLAN2 provides multiple levels, each capable of protecting against
`a certain percentage of bit errors.
`
` HiperLAN2 also employs multiple types of modulation. By dynamically adapting the FEC and
`modulation according to varying conditions, HiperLAN2 can transmit at higher data rates with a
`strong signal relative to noise; it can also transmit data at lower throughputs under adverse
`conditions.
`
` The next layer is the Data-link layer. In HiperLAN2, the Data-link layer is connection-oriented,
`which differentiates it from other wireless LAN technologies. Before a mobile terminal
`transmits data, the Data-link layer communicates with the access point in what is called the
`signaling plane to set up a temporary connection. This connection approach permits the
`negotiation of QoS parameters like bandwidth and delay requirements. It also assures that
`other terminals will not interfere with the subsequent transmission.
`
` By contrast, a mobile terminal that conforms to the IEEE 802.11 standards will communicate
`when the radio channel becomes available, and it may experience packet collisions from other
`terminals. It should be mentioned, however, that IEEE 802.11 does provide a separate
`mechanism for synchronous applications like voice.
`
` HiperLAN2 implements QoS through time slots. QoS parameters include bandwidth, bit error
`rate, latency, and jitter. The original request by a mobile terminal to send data uses specific
`time slots that are allocated for random access. Collisions from other mobile terminals can
`occur in this random-access channel, but since these messages are brief, this is not a problem.
`
`The access point grants access by allocating specific time slots for a specific duration in what
`are called transport channels. The mobile terminal then sends data without interruption from
`other mobile terminals operating on that frequency. A control channel provides feedback to the
`
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`sender, indicating whether data was received in error and whether it needs to be
`retransmitted.
`
` Above the Data-link layer is the Convergence layer, which responds to service requests from
`higher layers and formats data as required. This layer supports both packet-based (Ethernet) or
`cell-based (ATM) communications. When implemented for Ethernet, the Convergence layer
`preserves Ethernet frames and uses either conventional best-effort communications or the IEEE
`802.1p priority scheme.
`
` HiperLAN2 also comes with Automatic Frequency Allocation (AFA). To provide continuous
`coverage, access points need to have overlapping coverage areas. Coverage typically extends 30
`meters indoors and 150 meters in unobstructed environments. Access points monitor the
`HiperLAN radio channels around them and automatically select an unused channel. This
`eliminates the need for frequency planning and makes deployment relatively straightforward.
`
` When a mobile terminal roams from the coverage area of one access point to another, it
`initiates a handoff to the new access point after detecting a better signal on another radio
`channel. The new access point obtains details of the mobile terminal’s connection from the old
`access point, and communications continue smoothly.
`
`HiperLAN secures communications for a mobile terminal, creating a session (called an
`association) with an access point by first using a Diffie Hellman key exchange to negotiate a
`secret session key, then a mutual authentication process via either a secret key or a public key,
`if a PKI is available. Data traffic is encrypted using DES or Triple DES.
`
` With these security mechanisms, communication over HiperLAN should be as secure—if not
`more so—as over a wired LAN.
`BLUETOOTH
`
`Whereas HiperLAN2 is a powerful LAN technology, Bluetooth connects devices in a user’s
`immediate vicinity.
`Bluetooth promises to be an industry force. Its major selling points are its extremely low cost (it
`may eventually go as low as $5 per device) and its impending ubiquity (huge numbers of
`devices will soon incorporate it).
`
`In addition, Bluetooth enjoys wide industry support from approximately 1,400 companies that
`now belong to the Bluetooth Special Interest Group (SIG). And unlike most other wireless
`technologies, Bluetooth does not have direct competition (other than cables). The Bluetooth
`specification could become an official standard if adopted by IEEE 802.15, which seeks to
`develop a standard for Personal Area Networks (PANs).
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`The connections enabled by Bluetooth will be quite novel: headsets to cellular telephones;
`cellular telephones to portable computers; electronic wallets to point-of-sale systems; portable
`computers to Internet connections in airports or hotels, and on and on.
`
` In a world of computerized electronic gadgets, Bluetooth will not only be indispensable but will
`also make other technologies, such as cellular data, more attractive by making them easy to
`use.
`
` Bluetooth was designed to be inexpensive and to fit into a single 9-millimeter-by-9-millimeter
`microchip, and could eventually be designed into a variety of devices, whether mobile or
`stationary. However, Bluetooth only permits a small number of devices to engage primarily in
`point-to-point communications at medium speeds.
`
` The key architectural element of Bluetooth, the piconet, consists of up to eight devices. One
`device is designated the master, while the rest are slaves. The master is the device that initiates
`communication. Most devices will be capable of being either masters or slaves.
`
` Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) at the Physical layer, which means
`that by using different hopping sequences, multiple piconets can operate in one area and not
`interfere with each other. The master chooses the hopping sequence, which operates at 1,600
`hops per second. This is significantly faster than in most frequency-hopping wireless LANs.
`
` The master controls communication through a polling protocol. All communication is between
`a master and a slave, and the only way one slave device can communicate with another is via
`the master. Within one piconet, asynchronous data can be transmitted at a rate of up to
`721Kbits/sec, with 57.6Kbits/sec available in the return direction, or up to 432.6Kbits/sec in
`symmetric operation. One piconet also supports up to three voice channels at 64Kbits/sec each,
`though use of all three voice channels fills the capacity of the piconet.
`
`Rather than using separate send and receive frequencies, Bluetooth uses the same frequency
`for sending and receiving via Time Division Duplexing (TDD). TDD enables the same device to
`easily be a master or a slave. In fact, a device can be a master of one piconet and a slave to
`another.
`
`Time Division Multiple Access (TDMA) enables both asynchronous and synchronous
`communication. The master allocates slots according to the type of communication. For
`instance, synchronous voice channels require time slots at regular intervals, whereas data
`packets can be dispatched as slots become available. FEC and automatic repeat requests help
`protect against errors.
`
` The radio has a range of 10 meters, which is far enough for both personal devices and for other
`people’s devices. To restrict communications between desired devices, each Bluetooth machine
`has a Personal Identification Number (PIN). Users can specify what other PINs their devices can
`communicate with.
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` A maximum of eight devices in a piconet sounds restrictive, but some additional mechanisms
`extend the network. Though a piconet can only have seven active slave devices, an additional
`254 can be in a “parked” state, monitoring the network and ready to enter it. For example, a
`LAN or Internet POP could grant access to devices that have packets to send and receive, while
`keeping the rest in a parked state.
`
` It will also be possible to interconnect piconets into a “scatternet” that can include up to eight
`piconet masters and can support 20 voice channels. However, scatternets (along with proposed
`LAN emulation schemes) may be pushing the technology just a bit too far. The present
`specification just wasn’t designed for the complexity of LAN emulation or tying together a
`bunch of so-called scatternets.
`
` Bluetooth chipsets will be available in 2000 from a variety of chipmakers. The first products will
`roll out later in 2000, as well, but widespread use probably won’t occur until 2002. Once
`Bluetooth gains hold, you can expect it to become as ubiquitous as cordless phones and TV
`remote controls.
`
` Both HiperLAN and Bluetooth promise to have a tremendous impact on network connectivity,
`and users can look forward to a host of new products and services that will free them from the
`restrictions of a wired infrastructure.
`
`Resources
`The HiperLAN Alliance, at www.hiperlan.com, has information about the alliance and technical
`information about HiperLAN1.
`
`The HiperLAN2 Global Forum features information about the forum and technical information
`about HiperLAN2. Go to www.hiperlan2.com.
`
`Proxim is a market leader in wireless LAN products and the first company to announce a
`HiperLAN product. See www.proxim.com.
`
`The official Bluetooth Web site, www.bluetooth.com, contains information about the
`Bluetooth Special Interest Group (SIG) and the Bluetooth specification.
`
`Copyright 2000 CMP Media Inc.
`
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