Countdown to True Wireless Broadband 2, 2.5, 3, 3.5… 4G!

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AUGUST 2011: Of late, there appears to be more talk about looters than routers, and amidst burgeoning news about money made and lost, the real impact of 3G, if any, and the incumbent 4G technologies already on their way have been completely lost to all but serious tech-watchers. To the extent that the general population in India seems predominantly unaware of a relatively new term called broadband wireless access (BWA) that is being discussed extensively not just in developed nations but in the developing nations too. In fact, BWA is being positioned as a major shift in telecommunications and experts claim it could be more relevant than current broadband technologies for those at the bottom of the pyramid.

So, what is this BWA all about? Is it merely a wireless local area networking technology like Wi-Fi? Or, is it mobile Internet akin to code division multiple access (CDMA) or general packet radio service (GPRS)? Is it a second-generation (2G), third generation (3G) or fourth-generation (4G) mobile technology, or something else altogether? Is it an upgrade to any of the existing technologies or a new technology developed from scratch? Despite the BWA auctions having already happened in India, much of these details are still unclear to many.

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The true spirit of broadband
Broadband wireless access is essentially the addition of ‘broadband’ access to a wireless telecommunications network. What is so new about that? It sounds just like normal mobile Internet!

“That depends on what the definition of broadband is,” answers Dr Suresh Borkar of the electrical and computer engineering department, Illinois Institute of Technology, Chicago, who is also a senior principal investigator at Roberson and Associates, a technology and management consulting company in Chicago. He says, “The Telecom Regulatory Authority of India (TRAI) defines broadband as speeds greater than 256 kbps. This definition is woefully inadequate and outdated. The recent US FCC National Broadband Plan defines broadband as 100Mbps downlink and 50Mbps uplink.” The latest 4G technologies are chasing speeds as high as 1 Gbps.

With this clarification in mind, we can understand BWA to be a new generation of telecommunications technologies characterised by truly high-speed, always-on Internet delivered over higher bandwidth and wider area networks.

Predominantly, these new technologies or standards belong to either of the two streams. On one hand we have the 3GPP family, which includes the universal mobile telecommunications system (UMTS), high-speed packet access (HSPA) and long-term evolution (LTE) standards. On the other hand, we have the Institute of Electrical and Electronics Engineers’ (IEEE) 802.16x, commonly known as WiMAX.

“In the current scenario, the 3GPP technologies such as UMTS/HSPA/HSPA+ and LTE along with WiMAX and Evolution-Data Optimised (EV-DO) Revisions A/B are the available broad band wireless technologies, which are being deployed both in matured markets and in developing nations. Majority of the operators will adopt HSPA+ in near term. LTE deployment will have slow uptake and should mature in next three years as the ecosystem evolves. Video will strain the current BWA network and hence, prepare the stage for further upgrades on access and backhaul speed. New applications across different industry verticals will also be driving the broadband wireless access growth,” summarises Devaraj Srinivasan, general manager and head of R&D engineering practice – Global Media & Telecom business unit, Wipro Technologies.

Technologies in the BWA evolution
Current technologies such as GPRS, global system for mobile communications (GSM) and enhanced data rates for GSM evolution (EDGE), which brought in the trend of always-on mobile Internet, in a way marked the beginning of BWA. However, significant strides towards the BWA era will be made by 3G standards such as 3GPP/UMTS wideband code division multiple access (WCDMA), pre-4G standards such as HSPA, LTE Release 8 and Mobile WiMAX (802.16e), as well as real 4G standards such as HSPA+, LTE Release 10 and 4G WiMAX (802.16m).

Some salient features of BWA technologies
1. Larger networks, more bandwidth, more users, wider range
2. Multiple-input multiple-output (MIMO) systems
3. Multi-hop relays
4. Ad-hoc connectivity, automatic network configuration and self-organising networks (SON)
5. Co-operative multi-point transmissions
6. Adaptive array antennas that form wide-band beams
7. Antennas that can be tuned to multiple frequency bands; these antennas are designed for higher coverage, capacity and reliability
8. Priority management for public safety and defence applications
9. Multimedia broadcast, multi-cast service (MBMS)
10. Security enhancements
11. Flexible spectrum usage
12. Cognitive radios
13. Investments and research by telecom equipment makers to support higher capacity at lower costs

Universal mobile Telecommunications system (UMTS): 3G and 3.5G
A cellular technology developed by the 3GPP, UMTS can be considered as the start of real broadband wireless access, with up to 42Mbps speeds achievable in the Indian context. The UMTS standard provides specifications for the whole network, combining three different air interfaces—GSM’s mobile application part (MAP) core and the GSM family of speech codecs. While WCDMA-based UMTS networks are considered 3G, those that use HSPA are often referred to as 3.5G.

WIMAX base station
WIMAX base station

WCDMA. The 3G implementations of UMTS use WCDMA to offer greater spectral efficiency and bandwidth to mobile network operators. According to the Wikipedia, WCDMA is a wideband spread-spectrum mobile air interface that utilises the direct sequence spread spectrum method of asynchronous code division multiple access to achieve higher speeds and support more users compared to the implementation of time division multiplexing (TDMA) used by 2G GSM networks. In short, WCDMA improves upon the capabilities of 2G GSM networks. This probably explains why UMTS networks are often described as 3GSM networks. However, UMTS networks require new base stations and new frequency allocations, and do not directly build on the GSM standards like EDGE does.

HSPA. 3GPP’s HSPA is often known as 3.5G, as its mobile telephony protocols extend and improve the performance of WCDMA-based UMTS protocols through more efficient use of the broadband spectrum, and improved protocols and communication rules for the movement of voice and data packets between handheld de-vices and base stations.

HSPA combines two mobile telephony protocols—high-speed downlink packet access (HSDPA) and high-speed uplink packet access (HSUPA). Evolved HSPA (HSPA+) that is being used since 2010 uses the spectrum even more efficiently, allowing for higher peak data rates and fewer delays in data transmission. UMTS network with HSPA+ can easily reach speeds of 42 Mbps on a single 5×2 MHz carrier.

BWA networks demystified

Shyam Ananthnarayan, vice president – communications and wireless technology business, Tata Elxsi, explains some key features of BWA network infrastructure…

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A typical BWA network is usually composed of two key elements—base station and end-user subscriber equipment. The base station is typically realised as an indoor unit that uses outdoor antennas to send and receive high-speed data to and from the end user, and communicates with the core network through a single gateway. This is different from the traditional 2G/3G cellular systems that have been designed in a hierarchical manner with multiple nodes (network elements) to handle both circuit-switched voice and packet-switched data traffic.

Next-generation networks (NGN) such as WiMAX and LTE are based on flat IP architectures to support high-speed data traffic (Refer http://www.heavyreading.com/details.asp?sku_id=2180&skuitem_itemid=1097).

To efficiently deliver mobile broadband services, operators require a network infrastructure that simultaneously provides lower costs, lower latency, and greater flexibility. The key to achieving this goal is the adoption of flat, all-IP network architectures. With the shift to flat IP architectures, mobile operators can:
1. Reduce the number of network elements in the data path to lower operations costs and capital expenditure.

2. Partially decouple the cost of delivering service from the volume of data transmitted to align infrastructure capabilities with emerging application requirements.

3. Minimise system latency and enable applications with a lower tolerance for delay; upcoming latency enhancements on the radio link can also be fully realised.

4. Evolve radio access and packet core networks independently of each other to a greater extent than in the past, creating greater flexibility in network planning and deployment.

5. Develop a flexible core network that can serve as the basis for service innovation across both mobile and generic IP access networks.

6. Create a platform that will enable mobile broadband operators to be competitive, from a price/performance perspective, with wired networks.

7. Another key factor for the wireless network infrastructure setup is the network topology and the installation points for the base stations that serve subscribers/end users. In 4G networks that offer high-speed data services, the network topology is likely to be driven by the data backhaul considerations, keeping the low latency requirements for various applications in mind. Therefore, instead of large macro cells serving thousands of users, we are likely to see smaller micro and pico cells in metropolitan areas, with multiple base stations and outdoor antennas covering an area from just a few hundred metres to a few kilometres.

“3G evolution based on HSPA is one approach in the BWA evolution. Today there are more than 330 HSPA-capable mobile broadband networks serving more than 375 million users worldwide. Data rates of several Mbps are generally available and peak data rates as high as 80 Mbps are supported by the latest HSPA specifications. HSPA continues to evolve, and it will remain a highly capable and competitive radio access solution,” remarks Sanjay Dhawan, vice president, Ericsson India.

802.16m: The new WiMAX for the 4G world
Coming to the emerging 4G standards, for real broadband there are two main contenders, namely 802.16m WiMAX and LTE Release 10 (and above).

802.16m is an upgrade to the 802.16e standard, which is now popularly known as WiMAX. It has the same architectural framework and uses orthogonal frequency division multiplexing (OFDM) techniques as 802.16e, but promises significant improvements in cell capacity, user-experience and value-added service offerings. As against the current WiMAX speed of 40 Mbps, 802.16m can offer fixed speeds up to 1 Gbps. “In the Indian context, where only 20 MHz of time division duplexing (TDD) spectrum is available, 802.16m can offer only much lower speeds (e.g., 80-100 Mbps). However, the eco-system is almost non-existent today,” clarifies Dhawan.

Some of the key features of this upcoming standard are enhanced multiple-input-multiple-output (MIMO) modes, better interference management, optimised channel structure enhanced support for femtocells, introduction of relay stations, faster handovers, lower media access control (MAC) overhead, more efficient power-saving modes, enhanced multicast-broadcast services (MBS) and location-based services (LBS). Other enhancements include a slightly higher spectral efficiency, lower link access latencies, emphasis on both TDD and frequency division duplexing (FDD) operations, multi-radio coexistence and inter-technology handover, integrated multi-hop relay, better security, self organising and self-optimising base stations, additional target frequencies of operations, and so on.

WIMAX equipment
WIMAX equipment

It is claimed that 802.16m is completely backwards-compatible with its predecessor. Hence, although 802.16m requires new hardware that meets the specifications, 802.16e equipment can inter-operate with 802.16m equipment. This ensures smooth migration paths for 802.16e operators and inter-operability in roaming between both types of operators. However, some experts feel that the handover capabilities in 802.16e WiMAX are somewhat unproven and the migration path from 802.16e to 802.16m WiMAX is also somewhat questionable although not disruptive.

3GPP ITE release 10: Who will win the race?
The existing LTE standard—Release 8—is considered a pre-4G one. That is, it addresses a stage in the progression from 3G UMTS to 4G. However, forerunning implementations of Release 8, such as those by TeliaSonera in Sweden as well as AT&T and Verizon in the US, have been quite successful and so the bars are set quite high for the upcoming full-4G version—LTE Release 10 (also called LTE-Advanced). This is expected to be WiMAX’s biggest competitor, and many experts are betting on it winning the race, while others think the two will coexist for the consumer’s good.

“LTE meets, and in most cases exceeds, the requirements for a 4G technology. Through a range of innovative functionalities, LTE enables operators to manage more traffic and meet growing data-rate demands, and is consequently a key enabler for future mobile broadband delivery,” says Dhawan, adding that LTE-Advanced also supports speeds of 1 Gbps or more

LTE is an OFDM-based radio-access technology that supports up to 20MHz scalable transmission bandwidth and advanced multi-antenna transmission including beam-forming and spatial multiplexing, with up to four transmit antennas in the downlink direction. “LTE uses OFDM access for downlink but single-carrier FDMA (SC-FDMA) for uplink,” adds Dr Borkar.

Quick look: WCDMA vs OFDMA technologies

“Clearly WCDMA is less advanced and less efficient compared to newer OFDM technologies like WiMAX and LTE,” says Shyam Ananthnarayan. Here is why…
1. WCDMA technology is now able to give only up to 16 quadrature amplitude modulation or QAM (4 bits per symbol) whereas LTE based on OFDM already delivers 64 QAM (6 bits per symbol) and soon will deliver 256 QAM (8 bits per symbol). That means OFDM clearly delivers more bits per hertz of spectrum.

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2. Most modulation schemes lose bits in error correction schemes. Here also OFDM beats WCDMA.

3. OFDM-based technologies incorporate other advanced techniques like MIMO, smart antenna, sub-channelisation, etc, which increase the efficiency of these modulations in delivering high throughputs compared to WCDMA.

4. WCDMA involves chip-rate processing where every symbol will have to be multiplied by a large number, as large as 3,840,000 chips, requiring huge processing hardware, making the equipment and handsets power hungry. That means your battery drains faster, makes them bulkier and more expensive.

5. The base stations for current WCDMA sites use up to 6000 watt of power, whereas one can build LTE base stations that use 500 watt or less. In many emerging countries, this 10X advantage in power consumption makes a huge difference because most cell-sites take up huge cost in air-conditioner housing, generators, battery backup, power management systems, etc.

Like 802.16m WiMAX, LTE also has a single cell geographical coverage subject to the same frequency of operation, simplified flat packet transport based architectures, adaptive modulation to maintain consistent bit error rate, hybrid-automatic request and cyclic prefixing for handling transmission errors, and so on. However, while WiMAX is more data-centric for fixed and nomadic applications, LTE is more focused on mobility and wide area coverage. LTE has a legacy of design and deployment experience in the mobility arena since it comes from the mature 3GPP family of technologies.

“LTE is the fastest developing system in the history of mobile communication. In its first year, LTE usage soared from zero to 150 million people who have access to LTE networks today. Ericsson has supplied the large majority of these commercial LTE networks and has signed contracts with five of the top ten ranked operators by global revenue in 2010. Verizon’s LTE network is the world’s largest commercial installation to date. Just like the world’s first LTE network, launched by TeliaSonera in Sweden, it was supplied by Ericsson,” says Dhawan.

Just as WiMAX 802.16m is backward-compatible with its predecessor, LTE Release 10 is also backward-compatible with LTE Release 8. However, both LTE and WiMAX are not backwards-compatible with older networks. “In contrast to WCDMA/HSPA, LTE uses only packet core. Also, its modulation and access being OFDM in contrast to CDMA for WCDMA/HSPA, it is a disruptive technology with respect to these earlier 3GPP standards. Hence, compatibility/migration is not possible,” explains Dr Borkar.

Quick look: LTE Release 10 vs 802.16m WiMAX

1. OFDM. Both LTE access and WiMAX access are OFDM-based technologies and they operate at a frequency band different from current 2G/3G systems.

2. IP-based flat architecture. The core network architecture for both is flat IP-based. The cores are converging onto a single platform, and some vendors are already providing single cores to handle 2G/3G and 4G (BWA) systems.

3. Voice and SMS. Both WiMAX and LTE are IP networks and do not support voice as a native capability. There was a proposal that LTE could make use of the voice capability of 2G/3G networks with VoLGA. But that proposal has been rejected by the International Telecommunications Union (ITU) and voice is only supported using an IP multimedia subsystem (IMS). However, in comparison with WiMAX, LTE is expected to be better in terms of voice and SMS support.

4. Interoperability. LTE is designed to co-exist with GSM, WCDMA and HSPA networks; just that the RAN needs to be upgraded in a phased manner (just like the recent 3G roll out was possible through an upgrade of existing GSM/EDGE networks in a phased manner). The non-3GPP WiMAX is not interoperable with GSM and WCDMA networks, yet.

5. Backward-compatibility. Both LTE as well as WiMAX are not backward-compatible with earlier 3G standards. However, LTE-Advanced will be backward compatible with LTE; and WiMAX 802.16m will be backward-compatible with 802.16e.

6. Transition. The ease of transition from an existing technology to a new one is a key consideration when moving from one generation to another. In cases where a service provider has an existing network with a large number of subscribers, a phased transition is expected. In such a case, the cost of upgrading the core network to support both old and new subscribers deserves consideration. Therefore, in Greenfield projects like rural broadband access, or private networks (for defence, public safety, smart grid, etc), we see WiMAX as a good option. However, for telecom operators covering dense deployments and having an existing 2.5G/3G network, LTE may be a better choice.

However, one advantage that both HSPA+ and LTE have over WiMAX is their interoperability with WCDMA and GSM networks. Experts feel that the coexistence of LTE, HSPA and other 3G technologies will ensure service continuity as LTE rollouts and subscriber uptake proceeds at different rates in different regions. Multi-standard radio equipment that can deliver LTE, WCDMA/HSPA and GSM all from a single base station are available. This gives mobile operators the freedom to balance voice and data traffic across their different networks efficiently, together with the ability to serve all subscribers, irrespective of their network or device, from the same radio base station.

TD-LTE: The latest 4G craze
The 3GPP portfolio now includes a TDD version of LTE, popularly known as TD-LTE or TDD-LTE. TD-LTE is capable of running on the same frequency band (2.6 GHz in the US) as WiMAX, which is also a TDD technology. This part of the spectrum is much cheaper and has much less traffic as compared to the one used by the regular FDD version of LTE.

TD-LTE is touted to have many advantages over the FDD one. Regular LTE networks carry two separate signals, one for data travelling in each direction, whereas TD-LTE works over a single channel, simply allocating upload or download bandwidth depending on what you do. Plus, TD-LTE is so similar to normal LTE that the same chip can be used for both, making it easy for device makers to adopt the new technology. What’s more, TDLTE is fully-compatible with existing GSM/HSPA technologies with support for seamless mobility between these technologies. It is possible to upgrade even earlier WiMAX networks to the 4G TD-LTE, unlike the incompatibility between normal LTE and WiMAX.

Not surprisingly, the 2011 episode of CommunicAsia seemed to suggest the gaining popularity of this new standard, which has a Chinese origin. Apple is also considering a TD-LTE device.

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Standards—on-the-mark, get-set, go!
“As per an Ericsson Consumer Insights study, out of nearly 5 billion people who are estimated to have mobile broadband by 2016, about 95 per cent will be served by HSPA, WCDMA and LTE networks,” says Dhawan.

The current distribution of the various standards varies significantly across different regions and countries. A significant part of the world still uses GSM/GPRS/EDGE as the primary broadband technology, being only in the very early stages of introducing 3G standards. Some advanced countries, however, are already in the maturity stage of UMTS/HSPA standards and in the initial stages of 4G WiMAX 802.16m and 3GPP LTE.

The strongest trend in the future is clearly for the LTE standard. Apart from using the latest techniques and technologies in modulation, multiple access, coding, routing, radio and antennas, LTE has the additional advantage of being the only preferred 4G cellular standard globally with support of all major operators, and has possession of the lucrative lower-level spectrum (e.g., 700 MHz in many countries). All of this makes it a very strong force in the BWA revolution.

Dr Borkar confirms, “In the foreseeable future the global market seems to be almost equally divided between GSM/GPRS/EDGE, WCDMA/HSPA, LTE, and WiMAX with the first two declining, LTE expanding, and WiMAX comparatively stable or marginally increasing.”

“Whatever standard wins, there will be co-existence of UMTS/HSPA/HSPA+, WiMAX, Wi-Fi and LTE, and seamless session mobility and inter operability (at packet core) to meet the user-demand will be the way forward. Wireless spectrum availability always is a challenge and to address this, leveraging on all the access technologies will be the need of the hour,” says Srinivasan.

Does India have a special need for BWA?
Would India benefit in any specific way by the adoption of BWA technologies? Of course, say the experts. BWA will be very beneficial in covering the interior regions of India that are not yet covered by wired lines.

Transitioning to BWA networks

Transitioning to next-generation broadband wireless access networks requires upgrades in terms of the core network infrastructure, backhaul networks, devices and applications. A smooth transition also requires a clear migration path for operators.
1. Radio access network. UMTS, LTE and WiMAX require new RANs to be installed.

2. Backhaul networks. First to support the broadband access, we need to upgrade the speed of backhaul networks. From the current 10G Ethernet speed, it needs to be upgraded to 40G or even 100G. Upgrading to the highest speed will ensure that more base stations can be connected to the backhaul.

3. Devices. The availability of BWA devices at affordable costs will increase more penetration and acceptance of the technology. Users would typically require access devices such as USB dongles, mobile devices with built-in 4G modems (e.g., phones and iPad), or fixed wireless modems at home for BWA. Several products using WiMAX 802.16e are already available today, and 4G WiMAX products will also be available soon. In the case of LTE too, market leaders like Samsung, LG and Ericsson have launched a few chipsets for the pre-4G version, while a lot more chipsets and devices are currently in the development/trial stage for LTE-Advanced. The availability of LTE devices is on the rise, and prices are expected to see a downward movement from 2012 going forward.

4. Applications. The availability of rich applications that will completely utilise the abilities of BWA networks will speed up the adoption of such technologies.

5. Migration path for 3G operators. A clear migration path for 3G operators to move into 4G by reusing as much of the core and service infrastructure network elements needs to be clearly laid down. There is a clear migration path available for operators to move from 2G to 3G UMTS to LTE if they have adopted 3GPP family of products. Transitioning from 3G to 4G will be easier for operators using 3GPP technologies than WiMAX ones. WiMAX is more likely to be adopted by new operators than existing ones.

“Not only the interiors, but entire India has the need for BWA since even in major cities, wired network has very limited coverage. As part of leap-frogging technology from the current outdated systems (34 million wire-line customers across the country and the wireless technology being the 2G technology from the early 1990s), BWA is imperative for India if the country wants to grow. Depending upon the strategies of investment and migrations, the 3GPP WCDMA/HSPA is very appropriate at the current time followed by the 3GPP LTE at a suitable time in future, augmented by WiMAX 802.16m at selected places. The key issue for deployment is the backhaul. In addition to the access and the core infrastructure, backhaul is needed across all entities—access to core as well as across the whole public data network (PDN). Setting up an effective PDN is another major challenge,” says Dr Borkar.

He adds that in India, the transition to next-generation BWA networks is likely to be driven by service providers, who in turn are driven by consumer demand for data services and average revenue per user (ARPU) from data. The recent trends show that the demand for mobile data is showing a steady growth in the country. Therefore it is expected that the latest 4G technologies will be introduced in India in two to three years in the face of growing consumer demand. The challenges for service providers are more likely to be spectrum availability and short-term incentives to invest, particularly in rural areas where the ARPU is likely to be lower than in urban areas.

Shyam Ananthnarayan, vice president-communications and wireless technology business, Tata Elxsi, sums up, “BWA promises to help every section of the society through better access to information, education and new employment opportunities to Indians in both urban and rural areas. India has a special need for BWA to connect the people of every village, town, semi-rural, semi-urban and urban area to bring them on to one platform. It is expected that both WiMAX and LTE will find a place in a wireless nation. While LTE seems to be a natural migration path for operators in urban areas, WiMAX is likely to find a place in semi-urban and rural areas of the country.”


The author is a technically-qualified freelance writer, editor and hands-on mom based in Singapore

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