The electronics industry has been hearing a lot lately about the frenetic pace of the home-networking market. Much of the recent fanfare has centered on the 10-Mbit/s Lucent Technologies-Broadcom phone line networking proposal currently in its final stages of review by the Home Phone line Networking Alliance (HomePNA). The proposal's ratification should continue to position phone line networking as the quick-strike solution in the multifaceted home networking arena.
Following closely the deployment of phone-line networking technologies will be wireless home-networking implementations such as IEEE 802.11b HR (HR) LANs and networks based on Bluetooth, an emerging technology for enabling short-range, high-speed wireless communications between electronic devices. Lucent believes that home networks will evolve over time and, because it's unlikely that consumers will adopt a one-size-fits-all stance, the company provides a variety of wired and wireless solutions to tightly integrate voice and data communications. Because HomePNA and wireless LANs share a similar lineage, bridging between them is relatively straightforward when the proper hooks are built into the system-level solutions.
Wireless LANs have been available for more than a decade. Roaming untethered throughout a home, seamlessly connecting to information, is a very compelling prospect. It is even more compelling once the technology is driven to an attractive price point. The three principal standards-based contenders for the wireless home LAN market are HomeRF, Bluetooth and IEEE 802.11 wireless Ethernet.
All three operate in the unlicensed 2.4-GHz ISM (industrial, scientific and medical) band. One major difference among 802.11, HomeRF and Bluetooth is that both 802.11 and HomeRF employ connection or access points in their primary configurations to control LAN operation. In contrast, Bluetooth has developed ad hoc networks called piconets, which are created as required and consist of up to eight nodes, any of which can be a slave or master. Both 802.11 and HomeRF are also capable of ad hoc networking. Bluetooth and HomeRF include separate cordless phone-like voice channels, whereas 802.11 includes voice Quality of Service (QoS) capability as an option for its data channel.
Bell Labs has developed a proprietary QoS technology called Blackburst, a transparent media access control (MAC) overlay that provides time-bounded delay-access capability to carrier sense multiple access-type LANs, allowing QoS over phone line, 802.11 or wired Ethernet LANs. With Blackburst, 10 full-duplex, simultaneous, 32-kit/s voice channels would consume less than 6 percent of the bandwidth of an 802.11b HR LAN. This technology also supports the transfer of other types of time-bounded data, such as audio or video, and is being proposed to various standards groups.
Both Bluetooth and HomeRF were developed by industry Special Interest Groups (SIGs). Several major manufacturers have recently established a similar industry group, named the Wireless Ethernet Compatibility Alliance (WECA), to promote high-speed 802.11b HR interoperability testing and education. WECA has coined the name Wi-Fi, short for wireless fidelity, for 802.11b HR products. Another development expected to affect market success is the IEEE 802.15 working group's recent decision to consider Bluetooth for the Personal Area Network (PAN) standard.
The IEEE 802.15 working group was formed to develop MAC and physical interface (PHY) standards for short-distance wireless networks to support applications such as mobile workers. About 50 companies are taking part in the standard's development. One of the group's goals is to achieve a level of interoperability with 802.11 wireless LANs.
The IEEE 802.11 standard defines interfaces and protocols for wireless nodes to communicate with each other and/or with various access points on a network. The specification includes infrared, which is rarely used, frequency-hopping spread spectrum (FHSS) and direct-sequence spread spectrum (DSSS) options. One benefit of 802.11 devices is their support of complex MAC features, such as hidden nodes and roaming between application points. These features are required for enterprise applications but can be eliminated from home access points to minimize costs. Advances in semiconductor technology have enabled integration of these features on the client (PC) nodes with little or no cost increase.
First-generation 1-Mbit/s and 2-Mbits/s DSSS and FHSS products have been available for more than two years. Two extensions to 802.11, approved by the IEEE in September, are based on DSSS technology and increase the data rate significantly, now and in the future. IEEE 802.11b HR also operates in the 2.4-GHz ISM band and specifies 5.5- and 11-Mbit/s data rates. To achieve such high data rates, products being shipped use DSSS and complementary code keying (CCK) modulation. An even faster version, 802.11a, will operate in the 5-GHz band and specifies mandatory data rates of 6 Mbits/s, 12 Mbits/s and 24 Mbits/s, with optional data rates to 54 Mbits/s. This specification essentially reuses the HR 802.11b MAC, providing a clear path to speeds beyond 50 Mbits/s.
Essentially, the 802.11 standard was designed as a wireless extension to corporate LANs for enterprise applications; it is also being deployed in schools and universities and will be deployed in the future at public-access points. Home applications will leverage this deployment because the same 802.11-enabled PC can effortlessly connect to the various LANs provided the user has the right security handshake. An 802.11b HR wireless LAN transporting data at up to 11 Mbits/s dovetails nicely with the 10-Mbit/s HomePNA 2.0 specification. The high data rate is also a good match with new high-speed "fat pipe" access devices, such as cable modems and xDSL (digital subscriber line) modems that are beginning to show up all over.
The HomeRF SIG was organized to develop a wireless home-networking LAN specification for connecting PCs and peripherals. That spec, the Shared Wireless Access Protocol (SWAP), was released in the first quarter of 1999. First products are expected this year or early in 2000. HomeRF envisions PC-centric, SWAP-enabled networks, synchronized by control points and including printers, laptops and possibly some consumer electronics devices. HomeRF is based on first-generation FHSS 802.11 technology and adds optional voice capability derived from the Digital Enhanced Cordless Telecommunication (DECT) system's specification for limited-mobility cordless phones. First products are expected to support only data mode.
HomeRF developed its PHY by relaxing some of the 802.11 FHSS specifications, although it retains the 50-hops/s hopping rate to help avoid interference. It uses frequency-shift keying (FSK) modulation to deliver approximately 1 Mbit/s of data throughput. Like 802.11, a HomeRF network can conceivably support up to 127 nodes-the actual number is implementation-dependent-and up to four voice conversations. HomeRF specifies 100-mW maximum transmit power and a range of around 50 meters.
IEEE 802.11b HR is the only FCC-compliant wireless LAN standard that can run at over 10 Mbits/s. In an attempt to increase its data rate, the HomeRF SIG requested an FCC rule change to widen the operational bandwidths for 2.4-GHz FHSS devices. In response, the FCC issued a Notice of Proposed Rule Making soliciting comments on the change. This notice has ignited a firestorm of controversy as interested parties supporting and opposing the proposed change have filed their comments. The comments, including concerns that the requested change would increase interference between devices and increase the cost of products, are public records that can be accessed under Docket 99-231 from the FCC's Web site (www.fcc.gov).
The Bluetooth SIG was created to quickly develop a de facto standard to meet the communication needs of new mobile devices. The SIG has developed a specification for a small, very low-cost, low-power, short-range radio for a wide range of computing, telephony and consumer devices. The price goals for Bluetooth are clearly in line with widespread consumer deployment. The typical user profiles include sending e-mail from a laptop over a cellular phone, connecting a printer or fax machine to a PC and linking a PC or cell phone to a cordless headset.
Integrated transceivers with Bluetooth functionality will allow laptops, organizers, PCs and phones to communicate together in piconets. Because Bluetooth was initially intended for short-range communications, a number of power modes have been defined. Initial products are expected to provide 0-dBm transmit power, resulting in an effective range of about 10 meters. The specification also includes an optional higher transmitter power of 20 dBm, making it similar to HomeRF in distance capability.
Robust and resistant
Bluetooth's FHSS radio uses FM modulation combined with a very high 1,000-hop/s rate, which should make it very robust and more resistant to interference than 802.11 FHSS and HomeRF radios, which hop at 50 hops/s. The standard supports both voice and data with a maximum asynchronous data transfer rate of 721 kbits/s and up to three 64-kbit/s voice channels. Multiple piconets can be aggregated.
One concern affecting the coexistence of 802.11, HomeRF and Bluetooth is that devices operating close to one another can interfere, resulting in a loss of data packets to one or both networks. This is a major concern, especially when the networks support isochronous traffic such as voice or video. Evaluation work conducted by members of 802.11 and the HomeRF and Bluetooth SIGs indicate that the performance degrades gracefully as the amount of interference increases.
Discussion continues about the market position of HomeRF vs. the well-established 802.11 standard and Bluetooth's impressive market momentum. HomeRF was created to reduce costs of 802.11 LANs for the home at a time when 802.11 network interface cards cost more than $300 per node. In the time it has taken to develop HomeRF products, 802.11 products have dropped significantly in price. Recent announcements for 802.11b HR-based products for the home and costing as little as $99 for the interface card and $299 for the access point have positioned 11-Mbit/s 802.11b products at HomeRF's 1-Mbit/s targeted price points.
HomeRF and Bluetooth also overlap. Many people consider Bluetooth a wireless LAN even though it isn't officially defined as one and does not support peer-to-peer networking. Its raw data rate and voice quality are similar to HomeRF's, while its price target is significantly lower. Unlike HomeRF, the Bluetooth SIG 's founders include major cellular phone manufacturers. Lucent believes this will provide an opportunity for Bluetooth to build a strong user base as an interface between mobile devices, which should help drive down cost even before the home wireless LAN market takes off.