The understatement of the decade
It's probably the understatement of the decade to say that cell phones have become the single greatest tool in business. In today's world the ability to communicate with business associates while on the go is not just an advantage, it's a necessity. And because of that, the choices we make when choosing our handheld devices matter more than ever.
When it comes time to select a cell phone, the major part of the evaluation we make focuses on the features and benefits of the handset. Does it provide access to the Internet and email? Does it contain an organizer that will sync with Outlook, so you can take your scheduler, contacts, and information on the road? And most importantly, does it look slick?
But if you conduct a lot of your business on the road or internationally, the most important decision you make regarding your service may not have anything at all to do with the features we usually consider important for handhelds. Your choice of carrier and the technology it uses for its network might make the difference between being productive or ending up out of area.
The Major Carrier Technologies
The two major terms that pertain to cellular phone communication that you're likely to run into are GSM(Global System for Mobile Communications) and CDMA(Code Division Multiple Access), the two major technologies service providers use to carry voice signals across the network. But what are they and why do they matter? Selecting among these technologies as carrier for your cell phone is very important . Well, for starters, let's define the terms.
GSM (Global System for Mobile Communications).GSM is the "branded" term referring to a particular use of TDMA (Time-Division Multiple Access) technology. GSM is the dominant technology used around the globe and is available in more than 100 countries. It is the standard for communication for most of Asia and Europe. GSM operates on four separate frequencies: You'll find the 900MHz and 1,800MHz bands in Europe and Asia and the 850MHz and 1,900MHz (sometimes referred to as 1.9GHz) bands in North America and Latin America. GSM allows for eight simultaneous calls on the same radio frequency and uses "narrowband" TDMA, the technology that enables digital transmissions between a mobile phone and a base station. With TDMA the frequency band is divided into multiple channels which are then stacked together into a single stream, hence the term narrowband. This technology allows several callers to share the same channel at the same time.
CDMA (Code Division Multiple Access).CDMA takes an entirely different approach from GSM/TDMA. CDMA spreads data out over the channel after the channel is digitized. Multiple calls can then be overlaid on top of one another across the entire channel, with each assigned its own "sequence code" to keep the signal distinct. CDMA offers more efficient use of an analog transmission because it allows greater frequency reuse, as well as increasing battery life, improving the rate of dropped calls, and offering far greater security than GSM/TDMA. For this reason CDMA has strong support from experts who favor widespread development of CDMA networks across the globe. Currently, you will find CDMA mostly in the United States, Canada, and North and South Korea. (As an interesting aside, CDMA was actually invented for the military during World War II for field communications.)
CDMA is a "spread spectrum" technology, allowing many users to occupy the same time and frequency allocations in a given band/space. CDMA (Code Division Multiple Access) assigns unique codes to each communication to differentiate it from others in the same spectrum. In a world of finite spectrum resources, CDMA enables many more people to share the airwaves at the same time than do alternative technologies.
The CDMA air interface is used in both 2G and 3G networks. 2G CDMA standards are branded cdmaOne and include IS-95A and IS-95B. CDMA is the foundation for 3G services: the two dominant IMT-2000 standards, CDMA2000 and WCDMA, are based on CDMA.
Code Division Multiple Access, or CDMA, is technology for wireless cellular networks. The phrasing "Code Division Multiple Access" refers to this technology's approach of using special codes to spread information (i.e. voice and data calls) from different users across a large band of radio spectrum, allowing more calls and more data to travel over the same radio spectrum assigned. This means more users can be served by fewer cell sites.
CDMA 2000, an evolving technology
Since its launch in 1995, CDMA has proven to be a viable technology for wireless voice networks. Originally supporting high capacity voice and circuit switched data, it has since evolved into much more. It introduced the use of wireless technology in transmitting data at high speeds.
CDMA's major product iterations include cdmaOneT, CDMA2000, CDMA2000 1X and CDMA 2000 1x EV-DO.
1X was the critical first step in improving network performance and increasing voice and data capacity.
1XEV-DO, primarily a software upgrade to 1X with minimal need for component switch-out, is what truly allows service providers to offer advanced quality of service capabilities and data speeds that rival those delivered by wire line networks. 1XEV-DO enhancements meet the current growing demand for mobile IP multimedia services like "anytime, anywhere" Internet access, e-mail, video, mobile IPTV, gaming and voice and video conferencing, etc.
EV-DO Rev. A also makes it possible for CDMA carriers to introduce high-quality VoIP (Voice over Internet Protocol) to their customers.
1xEV-DO Rev. 0 enabled true 3G capabilities while 1xEV-DO Rev. A supports peak network speeds 130% faster than the speeds which qualify as 3G according to the ITU-R "IMT2000" definition.
Meanwhile, the next evolutions of CDMA are already underway. They will be known as 1xEV-DO Revisions A+ and B, and they will push efficiency and speeds to the next level, optimizing mobile broadband services for the user and tripling the current 1xEV-DO forward and reverse link peak data rates. All versions of the 1xEV-DO CDMA standards offer efficient spectrum assignments, which afford service providers a simplified migration to LTE (Long Term Evolution).
B. DESCRIBE THE IMPORTANCE OF TECHNOLOGY-
Though CDMA's application in cellular telephony is relatively new, it is not a new technology. CDMA has been used in many military applications, such as:
- Anti-jamming (because of the spread signal, it is difficult to jam or interfere with a CDMA signal).
- Ranging (measuring the distance of the transmission to know when it will be received).
- Secure communications (the spread spectrum signal is very hard to detect).
Besides using CDMA carrier for your daily calls,it has a vast use in the form providing you internet connectivity.
CDMA offers a world of oppurtunities for multimedia services, satellite communication, wireless local loop like e-mail, messaging, social networking, mobile internet, music and entertainment.
CDMA2000 was designed with the mobile Internet in mind. It is an efficient and reliable IP-based platform on which to deliver wireless data applications. EV-DO technologies, optimized for broadband data, were designed to provide high-speed user data rates - that are faster than fixed-line broadband solutions - and low latencies to enable a broad range of data, multimedia and delay-sensitive services to ensure a superior customer experience. CDMA2000 supports thousands of applications across multiple execution environments (e.g., BREW, Java, Linux, Palm, RIM, Windows Mobile, etc.) and customers can choose from a wide variety of handsets, fixed wireless phones to access these applications.
Today, CDMA2000 operators offer thousands of applications targeting consumers, businesses and public service organizations.
- Consumer: Popular consumer applications include short messaging, instant messaging, picture messaging, mobile TV, music downloads, video downloads, online gaming with richly rendered 3D graphics, and location-based services.
- Business: The business customer benefits from having high-speed data connectivity to the Internet and their virtual private network (VPN), and services such as sending and receiving e-mail with large attachments, push-to-talk and multimedia (PTT and PTM), and sales force automation functions.
- Public Service: The above services are also valuable tools for the public sector, including national security, first-responder and public safety users. Providing universal access to telephony and Internet services is a key economic priority for most governments. In many countries, EV-DO wireless broadband technologies are being deployed as a more economical DSL substitute. Forward looking governments are taking full advantage of these services by connecting schools, hospitals, medical clinics, police stations and communities to CDMA2000 telecommunication networks.
- If the future of wireless is 3G, then the future is also CDMA. Code Division Multiple Access is the basis for the three IMT-2000 technologies that are most widely supported worldwide: CDMA2000, WCDMA and TD-SCDMA. And of those three, CDMA2000 has attained the fastest momentum. CDMA2000, the first IMT2000 technology to be commercially deployed (in October 2000), now boasts 40 networks in 22 countries on 5 continents, and shows no signs of slowing down.
- CDMA2000 was first launched in South Korea, and in the two-and-a-half years since, operators across Asia, Australia, Europe, the Middle East, North and South America have deployed CDMA2000 systems.
- As of December 2002, there were nearly 33 million subscribers, growing at a rate of 3 million per month. 22% of all CDMA subscribers are 3G users today, and in some markets such as South Korea, CDMA2000 penetration accounts for 50% of all CDMA subscribers.
- The market for CDMA2000 continues to expand. Though some have expressed doubts about the need for and consumer interest in 3G, CDMA200 carriers are seeing phenomenal uptake of the innovative services and devices they are offering.
- With CDMA2000 1X, which has average data throughput of 60-100 kbps, operators are seeing data revenue increase more than 100 percent, and data ARPU many times that of 2G customers. With CDMA2000 1xEV-DO, an enhancement that offers average data speeds of 490-600 kbps, revenues are even higher.
- Some of the high-speed applications that CDMA2000 operators offer today include Internet browsing, m-commerce, multimedia messaging services (MMS), streaming video and video telephony. Picture trading, downloading movie previews, and GPS-enabled location-based applications are just a few examples of services available now that have unlimited opportunities for both the consumer and the enterprise user.
- "And there is no shortage of CDMA2000 devices on the market: more than 280 models from 35 vendors give subscribers a broad choice of features and price points from which to select."
- The strong performance of CDMA2000 has proven the demand for 3G. Market opportunities for advanced services will only increase. CDMA2000 has led the industry to this point, and will play a principal rote for years to come.
D. SECURITY ISSUES-
- In CDMA it has a single master key called the A-key which is used for authentication procedures.
- The A-Key is programmed into the mobile and is stored in the Authentication Center (AC) of the network.
- In addition to authentication, the A-Key is used to generate the sub-keys for voice privacy and message encryption.
- A-key known only by the Service Provider and the MS
- CDMA network security protocols rely on a 64-bit authentication key (A-Key) and the Electronic Serial Number (ESN) of the mobile.
- Some of the terms frequently used in CDMA systems are
ESN (Electronic Serial Number)
- Every mobile on the system is uniquely identified by the Electronic Serial Number (ESN) which is a 32 bit number pre-programmed at factory setting by the mobile phone manufacturer.
- The ESN is used to identify a mobile on the network.
Authentication in CDMA systems
- At the heart of the Authentication model in CDMA is the Authentication key or A-key which is like a master key to the system.
- The A-key is a 64 bit number stored in the mobile station and is usually pre-programmed at factory settings.
- The CDMA networks make use of a cryptographic algorithm known as CAVE or Cellular Authentication and Voice Encryption which is used in various stages of the procedure.
- This algorithm is used to generate a 128-bit sub-key called the "Shared Secret Data" (SSD).
- On the initiation of a SSD generation the Home Location Register/Authentication Centre (HLR/AC) sends out a Random number RANDSSD (56 bits) as a challenge.
- The A-Key, the ESN and the network-supplied RANDSSD are the inputs to the CAVE that generates SSD.
- The generated SSD is a 128 bit pattern, which is a concatenation of two 64-bit subkeys: SSD_A and SSD_B.
- The above steps are followed by a procedure known as Global Challenge.
- In this process the SSD_A is further fed into the CAVE algorithm along with ESN and MIN and a random number known as RAND (32 bits) which is now generated by the MSC.
- The result computed as Authentication Signature (AUTHR) (18 bits) is sent back by the mobile to the network.
- The network too would have calculated its own version of AUTHR which it uses to compare the result.
The network Base Station permits access to the mobile if the Authentication Signatures match and denies access if they do not.
Voice, Signaling and Data Privacy
- The mobile uses the SSD_B and the CAVE algorithm to generate
- Voice Privacy is provided by changing the characteristics of the Long PN Code which is used for spreading the Voice on the Traffic Channel.
- The SSD_B is fed into the CAVE algorithm along with the RAND and ESN to generate a 520 bit Voice Privacy Mask (VPM).
- The last 40 bits of this VPM is used as Private Long Code Mask (PLCM) in both the mobile and the network to change the characteristics of a PN Long code.
- This modified Long code is used for voice scrambling, which adds an extra level of privacy over the CDMA air interface.
- The SSD_B along with the RAND and ESN generates a CMEA (Cellular Message Encryption Algorithm) key (64 bits) which is then used on the E-CMEA (Enhanced CMEA) algorithm to encrypt the signaling messages sent over the air and to decrypt the information received.
- SSD_B is also fed into a Data Key Generator along with the RAND to generate the Data key.
- The Data key is used to encrypt and decrypt Data messages using the ORYX algorithm.
a Private Long Code Mask
a Cellular Message Encryption Algorithm (CMEA) key (64 bits)
a Data Key (32bits).
There are many existing security threats to Wireless Broadband networks with new threats appearing everyday and continue to be on the rise. A wireless broadband network requires a holistic end-to-end approach in order to secure the various nodes and signaling links within the network. In other words, it is not just about "securing the box"; it's about securing the entire network through a layered defense approach. CDMA air interface technology is inherently secure for protection of signaling and bearer traffic with excellent security in service provisioning for handset and parameter distribution. In addition, Nortel Switched Firewall, Threat Protection Systems and Application Switch can be utilized in the future to quickly protect the network from new threats when they are introduced. Today's service providers realize the importance of implementing security policy enforcement measure through software control for network elements, processes, best practices and physical control to allow subscribers peace of mind while fully benefiting from the Wireless Broadband Services. Nortel's layered security architecture and strong portfolio of security product protects your network, your subscribers, and your business.
CDMA has several unique features that make it a cost-effective, high quality wireless solution. In this module you will learn what those features are and how they provide advantages.
Power control is a CDMA feature that enables mobiles to adjust the power at which they transmit. This ensures that the base station receives all signals at the appropriate power.
The CDMA network independently controls the power at which each mobile transmits.
Both forward and reverse links use power control techniques.
Why power control is needed
If all mobiles transmitted at the same power level, the base station would receive unnecessarily strong signals from mobiles nearby and extremely weak signals from mobiles that are far away. This would reduce the capacity of the system.
This problem is called the near-far problem.
The multi-path problem
Signals sent over the air can take a direct path to the receiver, or they can bounce off objects and then travel to the receiver. These different paths, called multi-paths, can result in the receiver getting several versions of the same signal but at slightly different times.
Multi-paths can cause a loss of signal through cancellation in other technologies.
Handoff in CDMA
Handoff is the process of transferring a call from one cell to another. This is necessary to continue the call as the phone travels.
CDMA is unique in how it handles handoff.
Types of CDMA handoff
CDMA has three primary types of handoff:
The type of handoff depends on the handoff situation.
A soft handoff establishes a connection with the new BTS prior to breaking the connection with the old one. This is possible because CDMA cells use the same frequency and because the mobile uses a rake receiver.
The CDMA mobile assists the network in the handoff. The mobile detects a new pilot as it travels to the next coverage area. The new base station then establishes a connection with the mobile. This new communication link is established while the mobile maintains the link with the old BTS.
Soft handoffs are also called "make-before-break."
CDMA hard handoff
A hard handoff requires the mobile to break the connection with the old BTS prior to making the connection with the new one. CDMA phones use a hard handoff when moving from a CDMA system to an analog system because soft handoffs are not possible in analog systems.
A Pilot Beacon Unit (PBU) at the analog cell site alerts the phone that it is reaching the edge of CDMA coverage. The phone switches from digital to analog mode as during the hard handoff.
Hard handoffs are also called "break-before-make."
When does CDMA use a hard handoff?
The CDMA hard handoff may be used when moving from a CDMA network to an analog one. It may also be used when moving to a different:
- RF channel
Advantages of CDMA
CDMA technology has numerous advantages including:
- Customer satisfaction
CDMA's features result in coverage that is between 1.7 and 3 times that of TDMA:
- Power control helps the network dynamically expand the coverage area.
- Coding and interleaving provide the ability to cover a larger area for the same amount of available power used in other systems.
CDMA capacity is ten to twenty times that of analog systems, and it's up to four times that of TDMA. Reasons for this include:
- CDMA's universal frequency reuse
- CDMA users are separated by codes, not frequencies
- Power control minimizes interference, resulting in maximized capacity.
CDMA's soft handoff also helps increase capacity. This is because a soft handoff requires less power.
Often CDMA systems can achieve "wireline" clarity because of CDMA's strong digital processing. Specifically:
- The rake receiver reduces errors
- The variable rate vocoder reduces the amount of data transmitted per person, reducing interference.
- The soft handoff also reduces power requirements and interference.
- Power control reduces errors by keeping power at an optimal level.
- CDMA's wide band signal reduces fading.
- Encoding and interleaving reduce errors that result from fading.
CDMA's better coverage and capacity result in cost benefits:
- Increased coverage per BTS means fewer are needed to cover a given area. This reduces infrastructure costs for the providers.
- Increased capacity increases the service provider's revenue potential.
CDMA costs per subscriber has steadily declined since 1995 for both cellular and PCS applications.
CDMA phones are usually dual mode. This means they can work in both CDMA systems and analog cellular systems.
Some CDMA phones are dual band as well as dual mode. They can work in CDMA mode in the PCS band, CDMA mode in the cellular band, or analog mode in an analog cellular network.
"Why is a dual-mode phone useful?
Sometimes users travel outside a CDMA network and need analog mode to use these systems."
CDMA results in greater customer satisfaction because CDMA provides better:
- Voice quality
- Longer battery life due to reduced power requirements
- No cross-talk because of CDMA's unique coding
- Privacy--again, because of coding.