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Choice of Platform: Wireless and wireline technologies to coexist

August 31, 2011

As consumer appetite for data increases, broadband networks will be required to deliver more bandwidth per user. Current assessments of traffic on the carrier backbone show that bandwidth requirements are doubling every 12-18 months and this growth rate is expected to continue in the near future. In addition, the increasing demand for high bandwidth applications and services such as VOIP, internet protocol television (IPTV), video-on-demand, file sharing, user-generated content, online gaming and social networking would continue to put pressure on the core network.

Consumers will need to use a mix of wireless and wireline broadband technologies for different applications. While wireline broadband would provide adequate bandwidth for a rich multimedia experience, wireless broadband would help meet their bandwidth-intensive mobile requirements.

The launch of broadband wireless access (BWA) services is expected to change the dynamics of broadband usage in the country. With the introduction of affordable smartphones and an increase in consumer awareness about these services, wireless broadband is expected to make a strong entry.

However, despite the excitement surrounding wireless broadband technology, wireline has not lost its sheen either. It continues to hold its own and remains the primary platform for broadband connectivity, delivering far higher data rates than wireless (up to 30 times higher). Given that applications such as IPTV and VOIP have high data requirements, the demand for wireline will continue to increase. The segment has witnessed significant development over the past decade, and technologies like fibre-to-the-home (FTTH) and next-generation cable modem have enhanced the speed and overall broadband experience.

Wireline broadband

The major wireline broadband mediums include digital subscriber line (DSL), fibre and cable modem. About 66 per cent of the global broadband connections are on DSL, 22 per cent are on cables and 11 per cent are on  FTTH.

Over the past 15 years, DSL has been the dominant broadband technology. For telephone companies, the core service has historically been voice, for which twisted pair copper cable has been the medium of choice. DSL technologies have allowed operators to provide broadband access over these copper cables.

DSL networks are normally divided into service areas where subscribers near the central office (normally within 1 to 3 miles) are served directly and other users are served from remote field terminals. The size of the service area depends on the type of DSL technology being used and the bandwidth requirement at the customer’s end.

DSL involves many technologies that are distinguished by data rates, reach and applications. These include asymmetric DSL (ADSL), symmetric DSL and very high-bit DSL. The ADSL family (ADSL, ADSL2+, ADSL2++) is the most commonly deployed DSL technology, with up to 20 Mbps downstream capacity and a peak upstream capacity of 1-3 Mbps.

ADSL lines cover distances of up to 5 km, enabling deployment from a central office. Copper loops in downtown areas of many cities are 2 km long, which corresponds to speeds of 16 Mbps. Operators are now capitalising on their existing copper networks and have started bundling IPTV offerings as well as VOIP with DSL broadband.

DSL has so far been the technology of choice for operators intending to utilise their existing cable network. For example, Bharat Sanchar Nigam Limited has benefited from its wide network, which was readily available for broadband services.

However, over the years, it has been realised that DSL technology has several limitations in terms of distance, compatibility, need for field electronics, electrical interference and a relatively modest broadband capability. Most service providers have realised that DSL cannot be a long-term solution for broadband service delivery.

With its capability to provide high bandwidth, optic fibre is quickly becoming the preferred internet backbone. Fibre offers far higher data rates and coverage than copper cables. Moreover, it can be deployed through point-to-point connections from a central access switch or an optical line termination to the subscriber’s premises or to a subtended DSL access multiplexer. Also, several subscribers may share fibre in passive optic networks.

Major solutions in this space include fibre-to-the-kerb and fibre-to-the-building, with FTTH being the final access solution where each subscriber is connected to a fibre.

Gigabit-capable passive optical network (GPON), ATM-based PON and active Ethernet are the three main FTTH technologies. Most GPON installations use optical splitters to serve up to 32 subscribers through a single fibre from the central office. GPON technology offers 2.4 Gbps downstream and 1.2 Gbps upstream speeds, which are shared by 16 or 32 customers on the same PON.

Active Ethernet systems use dedicated fibre networks between the central office and the customer. Consequently, the bandwidth consumption of one customer does not affect the amount of bandwidth available for other customers. In addition, active Ethernet systems are symmetrical as the downstream and upstream rates are the same. Currently, most of these systems can provide up to 1 Gbps speed to each subscriber, which is ten times higher than the bandwidth available on a GPON system.

Wireless broadband

There are three wireless communication mediums, which are classified on the basis of the distance they are meant to cover – wireless personal area networks (WPANs), wireless local area networks (WLANs) and wireless wide area networks (WWANs).

WLANs are designed to connect devices to wired networks. Unlike wired LAN, WLAN does not require cabling to connect the device to a switch or router. Devices connect wirelessly to nearby wireless access points that are attached to the local network using an Ethernet connection. Wi-Fi (or IEEE 802.11) is the set of standards established to define wireless LANs. Several protocols are defined in the 802.11 family of standards, which address various operating frequencies and throughputs. The 802.11g standard is currently the predominant protocol for WLAN implementation.

WWAN provides broadband data networks with a far higher geographical reach than WPAN and WLAN. It uses cellular technologies such as GPRS, HSPA, UMTS, 1xRTT, 1xEVDO and long term evolution (LTE). Wireless data devices connect to a wireless broadband network through a commercial carrier’s data network. 1xEVDO is the broadband wireless network standard developed by the Third Generation Partnership Project 2 (3GPP2) under the CDMA2000 family of standards. EVDO networks were first launched based on Release 0 of the standard. The standard is currently in Revision A, which provides average download speeds of 600 kbps to 1.4 Mbps, and average upload speeds of 500-800 kbps, with low latencies of 150-250 milliseconds.

WWANs have evolved from both CDMA and GSM platforms to LTE. GSM is a 2G technology that offers both voice and data capabilities and supports data transmission rates of up to 9.6 kbps. This enables applications like short messaging service and international roaming.

WCDMA brought GSM into 3G. It is a 3G cellular network and is a high speed transmission protocol used in UMTS. UMTS offers packet-based transmission for text, digitised voice, video and multimedia content.

The next mobile telephony protocol in the GSM to LTE evolution path is HSPA. HSPA helps in improving the performance of UMTS. The HSPA family has further evolved to HSDPA, HSUPA and HSPA+, which provide peak downlink speeds of up to 14.4 Mbps, 5.76 Mbps and 42 Mbps respectively.

On the CDMA front, the transition has taken place through 2G CDMA-based cdmaOne, CDMA2000 CDMA2000 1xEVDO, CDMA2000 1xEVDO Release 0 and the latest CDMA2000 1xEVDO Revision A. The latest standard supports the framework for quality of service, reduces latency, and offers peak speeds of 3.1 Mbps for download and 1.8 Mbps for upload.

LTE is the latest standard in the evolution paths of both CDMA- and GSM-based data networks. The technology supports both frequency division duplex and time division duplex (TDD) as well as flexible carrier bandwidths from below 5 MHz to up to 20 MHz. LTE also enables speeds of over 200 Mbps. Two entities, the 3GPP, representing the family of networks generally referred to as GSM, and 3GPP2, representing the family of networks generally referred to as CDMA, are working together to lay the foundation for LTE.

Many major global wireless carriers have selected LTE as the foundation for their 4G network deployment. These include Verizon Wireless, Vodafone, China Mobile, AT&T, China Telecom, KDDI, MetroPCS, NTT DOCOMO, and T-Mobile. In India, of the six winners in the BWA auction, key players like Bharti airtel, Infotel Broadband and Qualcomm have decided to adopt LTE as the 4G technology platform.

The main advantages of LTE include high peak speeds of 100 Mbps downlink (20 MHz, 2x2 MIMO), both indoor and outdoor, and 50 Mbps uplink. It is capable of supporting at least 200 active voice users in every 5 MHz. The platform has a low latency rate and offers four times the bandwidth provided by existing 3G systems.

Another technology that enables the provision of mobile broadband is Wi-Max. Mobile Wi-Max is competing with LTE to become the preferred mobile broadband technology. These technologies use the same fundamental wireless standard known as orthogonal frequency division multiplexing.

Fixed Wi-Max, standardised as IEEE 802.16-2004, has been playing a key role in providing fixed wireless broadband access and is an alternative to wireline ADSL in areas where ADSL is not available and carriers are unable to provide wireline broadband services in a cost-efficient manner. Driven by economies of scale and interoperability between vendors, the technology has evolved from the fixed version to support mobility through mobile Wi-Max 802.16e. In addition to mobility, mobile Wi-Max supports features that increase spectrum efficiency. It is the best TDD technology for fixed nomadic and mobile access aimed at the 2.3 GHz, 2.5 GHz and 3.5 GHz bands, and offers 40 Mbps peak bit rates for 10 MHz bandwidth, and up to 80 Mbps peak bit rates for 20 MHz bandwidth.

Wi-Max is being used as wireless backhaul for bandwidth-intensive applications such as wireless video surveillance and traffic synchronisation. In the future, it will be used as the backhaul technology for wireless voice and data networks as well.

Satellite broadband is another option for delivering wireless broadband services. The technology involves the use of geostationary satellites orbiting the earth at the same speed as the planet’s rotation. This technology has been deployed in areas with uneven terrain where it was difficult to deploy wireline networks. However, the quality of service offered by satellites is not comparable to that provided by wireline broadband or 4G services. Since the wireless signal has to travel a long distance, satellite broadband services have very high latencies and are not suitable for the delivery of interactive multimedia services.

To decrease latency, there have been efforts to deploy medium and low earth-orbiting satellites, where the satellites are only a few hundred miles to a few thousand miles above the earth.

Conclusion

As the quality of applications improves, content becomes more relevant and customised, and awareness about broadband increases, bandwidth consumption and consumer expectations for quality are expected to rise further. These quality improvements can be achieved only through the convergence of wireless and wireline broadband services. Convergence will also enable service providers to offer uninterrupted on-the-go broadband services. The shift towards building converged networks has gained momentum as operators try to minimise costs and offer consumers continuous broadband connectivity.

Though the evolution to a unified core network that supports existing access technologies in both the fixed line and mobile domains is likely to take time, it will determine an operator’s ability to reduce opex in the long term as well as increase competitiveness and profitability.

 
 

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