Big Dan's Security

Advantages of 802.11 Local Area Wireless Networks over 3G

Introduction of 802.11:

"Wireless LANs opens new possibilities for LAN users, which are mainly terminal mobility and easy reconfiguration. In general, wireless LANs has the following advantages": [J.H.Schiller,2000]

1. Flexibility: If WLAN nodes are within the network coverage area then they can communicate with each other without major limitations in terminal location. It is not important for the terminals to remain visible to each other. If the frequency of electro magnetic waves is not too high then the walls and other typical obstacles in an indoor environment are mostly penetrated.
2. Simplified planning:  Configuring a ad hoc network is not necessary and the network deigning part is related to radio engineering.
3. Possibility of a temporary network configuration: Networks which are needed temporarily can be set up using wireless communication. (E.g. during large international exhibitions, sport contests, etc).

"WLANs also have some disadvantages. Most of them are the result of using a radio channel as a signal propagation medium. The main disadvantages are the following":[Hazysztof Wesolowshi, 2002]

1. Lower transmission quality as compared with wire line LANs: 10^-3 – 10^-4 is the order of error in the radio channel or it can be worse than this. To achieve higher quality FEC or ARQ techniques are necessary. For comparison, the error rate for transmission over an optical fibre channel is at most 10^-10.
2. Lower safety and security: The information transmitted on radio channel can be easily intercepted when compare to wireline LANs. If WLAN is used inappropriately then it can become a source of interference for other sensitive devices such as medical equipment. Wireless LANs rarely work independently of other networks and, wireless transmission is used to access a wire line network.

Different generations in mobile phones:

1G:

1G is short form for first generation analog cellular technology (AMPS is one example of a 1G cellular system). Deployed during the 1980s, this technology has been designed to transmit voice phone calls from wireless handsets. Calls are transmitted in the air and are very easy to intercept. "1G (or 1-G) is short for first-generation wireless telephone technology, cellphones. These are the analog cellphone standards that were introduced in the 1980s and continued until being replaced by 2G digital cellphones. The main difference between two succeeding mobile telephone systems, 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G networks are digital."[http://www.nationmaster.com/encyclopedia/1G]

Circuit Switch:

Analogue circuit-switched technology system is used in 1G, with FDMA (Frequency Division Multiple Access), it works mainly in the 800-900 MHz frequency bands. The networks had a low traffic capacity, unreliable handover, poor voice quality, and poor security.

To send  signal from cell base station to the handset, systems typically allocated one 25 MHz frequency band, and another 25 MHz band for signals being returned from the handset to the base station. Now these bands are split into a number of communication channels, each of which is used by particular caller.

2G

After 1G, 2G (second Generation) mobile telephone came into existence. For the first time 2G introduces a mobile phone which works  purely on digital technology. The demands placed on the networks, particularly in the densely populated areas within cities, meant that increasingly sophisticated methods had to be employed to handle the large number of calls, and so avoid the risks of interference and dropped calls at handoffs. They are many common principles involved in both the generation phones. Such as, they both use the same cell structure. But the way the signals are handled are different. 1G network are not capable of providing the more advanced features of the 2G systems, such as caller identity and text messaging.

In GSM 900, for instance, two frequency bands of 25 MHz bandwidth are use. The band 890-915 MHz is committed to uplink communications as of the mobile station to the base station, and the band 935-960 MHz is used for the downlink communications as of the base station to the mobile station. Every band is separated into 124 carrier frequencies, spaced 200 kHz away from each other, in a similar manner to the FDMA method that was used in 1G system. Then, every carrier frequency is extra divided by TDMA into eight 577 usec long "time slots", each one of which represent one communication channel - the entire number of probable channels obtainable is therefore 124 x 8, producing a speculative maximum of 992 simultaneous conversation.

GPRS and EDGE

2.5G (Second Generation Enhanced) is a general term used to pass on to a standard of wireless mobile telephone networks that lies in between 2G and 3G. The growth of 2.5G has been view as a stepping-stone towards 3G, which was encouraged by insist for improved data services and right to use the Internet. In the development of mobile communications, each generation provide a advanced data rate and additional capability, and 2.5G is no exemption as it is provide quicker services than 2G, but not as fast or as sophisticated as the newer 3G systems.

Some observer have seen 2.5G as an substitute route to 3G, but this appear to be short-sighted as 2.5G is quite a few times slower than the complete 3G service. In technical provisions 2.5G extends the capability of 2G systems by providing extra features, such as a packet-switched connection (GPRS) in the TDMA-based GSM system, and enhanced data rates (HSCSD and EDGE). These enhancement in 2.5G systems allow data speeds of 64-144 kbps, which enable these phones to characteristic web browsing, the use of routing and navigational maps, voice mail, fax, and the transfer and receive of large email messages.

3G

Third Generation mobile telephone networks are the most recent phase in the growth of wireless communications technology. Important features of 3G systems are that they carry much higher data transmission rates and present increased capacity, which makes them appropriate for high-speed data application as well as for the customary voice calls. In fact, 3G systems are planned to process data, and as voice signals are transformed to digital data, these outcomes in speech being deal with in a Great Deal the similar way as any supplementary form of data. Third Generation systems utilize packet-switching technology, which is more capable and faster than the customary circuit-switched systems, but they do need a somewhat special infrastructure to the 2G systems. "Japanese 3G services were launched in 2001, making Japan one of the first countries to offer 3G technologies commercially. Japan's 3G technology is capable of matching the quality of fixed-line telecommunications devices whilst providing high-speed data transmission and global roaming to all areas where 3G networks exist."[The Wireless Telecommunications Market in Japan, April 2006]

W-CDMA and CDMA2000

It is usually accepted that CDMA is a greater transmission technology, while it is compared to the previous techniques use in GSM/TDMA. W-CDMA systems make more capable use of the accessible spectrum, because the CDMA technique enables all base stations to employ the same frequency. In the W-CDMA system, the data is divided into separate packets, which are then transmit using packet switching technology, and the packets are reassembled in the accurate sequence at the receiver end by means of the code that is transmitted with each packet. W-CDMA has a probable problem, because by the fact that, as more user at the same time communicate with a base station, then a event known as "cell breathing" can take place. This effect funds that the user will compete for the limited power of the base station's transmitter, which can decrease the cell's range – W-CDMA and cdma2000 have been planned to ease this problem.

UMTS

UMTS systems are planned to provide a range of data rates, depending on the user's conditions, providing up to 144 kbps for moving vehicles (macrocellular environments), up to 384 kbps for pedestrians (microcellular environments) and up to 2 Mbps for interior or immobile users (picocellular environments). In disparity, the data rates support by the vital 2G networks were only 9.6 kbps, such as in GSM, which was insufficient to provide any complicated digital services.

Modulation Techniques:

Process of altering some characteristic of a periodic wave with an external signal is known as modulation. These high frequency carrier signals can be transmit over the air without difficulty and are able to travel long distances. The characteristics (amplitude, frequency, or phase) of the carrier signal are wide-ranging in agreement with the in turn bearing signal. In the field of communication engineering, the in turn bearing signal is also identified as the modulating signal.

FDMA:

Frequency Division Multiple Access or FDMA is a type of channelization protocol used in multiple-access process. In FDMA users are allocated one or more frequency bands, giving them the opportunity to utilize the allocated band without with each other. Coordination of access is done between multiple customers using Multiple Access techniques. Different methods like TDMA, CDMA are also used by users to share access.

TDMA:

Time division multiple access (TDMA) is a shared medium access method of channel (usually radio) networks. It divides the channel in to different time slots and allows different users to share the same frequency channel. The users transmit rapidly  each using their own time slot on after the other. Only a part of the channel capacity is used to share the same transmission medium over multiple stations. GSM which is digital 2G technologies uses TDMA. It is also used in other systems like Personal Digital Cellular and iDEN, and in the system of Digital Enhanced Cordless Telecommunications which is a standard for portable phones

CDMA:

Many radio communication technologies use CDMA channel access method. Transmitting information at a time over single channel allowing many users is the main concept and idea in data communications. In this concept several transmitters share a bandwidth of frequency. This is called as multiplexing. Spread spectrum technology and coding scheme (where each user is assigned a code) which allows many users to get multiplexed on the same physical channel is employed in CDMA. In short FDMA divides access by frequency, TDMA divides it by time and CDMA which is a spread-spectrum and coding scheme divides access by assigning a code since a modulated coded signal has much higher data bandwidth than the data communicated itself. The codes assigned occupy the same channel, but the users associated with a code can understand each other.

3G and 802.11 Data Rates and Integration

Data rates of 3G compared to WLANs

The data rates of wireless LANs are anywhere from 1 Mbps to 54 Mbps. It is allowed by the 802.11 standards based on the distance to the access points. Access points can cover only a few thousand meters, making them suitable for small networks such as hotels and airports. When comparing wireless networks built using 3G standards require higher capital investment and support a data rate of around 64 Kbps to 2 Mbps as maximum, but covers a wide area range which enables ubiquitous connectivity. Architectures that allow users to normally shift between these two networks would be advantages and profitable to both service providers and users.

WLANs Integration with 3G networks.

The development of wireless communication has been rapid and it had been applied for many services. Wireless local area networks and cellular mobile networks have been the most useful technologies to use wireless communication.  3G networks cover wider areas with ubiquitous connectivity but with low-speed date rates. Wireless local area networks in turn cover small areas but with higher data rates and easy compatibility of wired internet. 3G and WLAN possess some complementary properties. Integrating these two networks will provide users high speed wireless data service and ubiquitous connectivity. Integration of these two networks involves several issues to be considered which are authentication, billing, QoS, and roaming with out interruption in between the networks.

The degree of inter-dependence one is introducing between these two networks, there are two methods of integrating them. They are:

1. Tightly-coupled internetworking
2. Loosely-coupled internetworking

Tightly-coupled Interworking

The concept behind tightly-coupled approach is that the 802.11 network should appear like another 3G access network to the main 3G network. In this the 802.11 network will imitate functions which are present in 3G core network. In the figure we can see that the 802.11 gateway uses WISP No.1 to imitate itself as PCF for 3G core network and in case of CDMA2000 network it appears as SGSN to UMTS. The gateway of 802.11 hides all details of 802.11 networks from 3G core and it tries to implement all 3G protocols required for a 3G access network. "Mobile Nodes in this approach are required to implement the corresponding 3G protocol stack on top of their standard 802.11 network cards, and switch from one physical layer to the next as needed. All the traffic generated by clients in the 802.11 network is injected using 3G protocols in the 3G core".[ M. Buddhikot, G. Chandranmenon, S. Han, Y. W. Lee, S. Miller, L. Salgarelli, 2003]

The unlike networks would divide the similar authentication, signalling, transport and billing infrastructures,  separately as of the protocols utilized at the physical layer lying on the radio interface. However, this advance presents quite a few disadvantages. As the 3G core network straight away expose its interfaces to the 802.11 network, one operator must possess both the 802.11 and the 3G parts of the network. In fact, in this case, separately operated 802.11 island cannot be integrated with 3G networks. Today's 3G networks are self deployed using cautiously engineered network-planning tools, and the ability and constitution of each network part is calculated utilizing mechanisms which are very much exact to the technology used over the air interface. By injecting the 802.11 traffic non-stops into the 3G core, the unit of the entire network, as fine as the constitution and the plan of network elements such as PDSNs and GGSNs has to be customized to maintain the increased load. The arrangement of the client parts also present many issues with this move.

"First, as described earlier, the 802.11 network cards would need to implement the 3G protocol stack. It would also mandate the use of 3G-specific authentication mechanisms based on Universal Subscriber Identity Module" or "Removable User Identity Module (R-UIM) cards  for authentication on Wireless LANs, forcing 802.11 providers to interconnect to the 3G carriers' SS7 network to perform authentication procedures". [Removable User Identity Module Standard for CDMA 2000 Spread Spectrum Systems, June 2000.]

This would also entail the use of 802.11 network interface cards with fixed USIM or R-UIM slots or external cards plug individually into the user devices. For the reason given above, the complication and the high price of the rearrangement of the 3G core networks and of the 802.11 gateways would push operators that choose the tightly-coupled approach to turn into uncompetitive to 802.11- only WISPs.

Loosely-coupled Interworking

Like the earlier architecture, the loosely-coupled draw near calls for the beginning of a new element in the 802.11 network, the 802.11 gateway. On the other hand, in this design, the gateway connect to the Internet and do not contain any straight link to 3G network essentials such as PDSNs, GGSNs or 3G core network switches. The users that access services of the 802.11 gateway may comprise users that have in the vicinity signed on, as well as mobile customers visiting from erstwhile networks. "We call this approach loosely-coupled interworking because it completely separates the data paths in 802.11 and 3G networks. The high speed 802.11 data traffic is never injected into the 3G core network but the end user still achieves seamless access. In this approach, different mechanisms and protocols can handle authentication, billing and mobility management in the 3G and 802.11 portions of the network. However, for seamless operation to be possible, they have to interoperate". [Wireless IP Network Standard. P.S0001-A-1, 2000]

In the case of interoperation with CDMA2000, this require that the 802.11 gateway supports Mobile-IP functionalities to hold mobility across networks, as well as AAA services to interwork with the 3G's home network AAA servers. This would allow the 3G provider to gather the 802.11 office records and make a unified billing statement representing usage and different cost schemes for both (3G and 802.11) networks. At the similar time, the utilization of well-matched AAA services on the two networks would permit the 802.11 gateway to dynamically get per-user service policies as of their Home AAA servers, and to implement and become accustomed to such policies for the 802.11 network. "Since the UMTS standard do not yet include support for IETF protocols such as AAA and Mobile-IP, more adaptation is required to integrate with UMTS networks. Mobile- IP services would need to be retrofitted to the GGSNs to enable seamless mobility between 802.11 and UMTS. Common subscriber databases would need to interface to Home Location Registers (HLR) for authentication and billing on the UMTS side of the network, and to AAA servers for the same operations to be performed while clients roam to 802.11 networks. There are several advantages to the loosely-coupled integration approach. First, it allows the independent deployment and traffic engineering of 802.11 and 3G networks".[ IP Mobility Support for IPv4, January 2002]

Conclusion.

In this paper, I described the issues in the integration of third-generation wireless networks with local-area wireless technologies such as 802.11. In that introduction of two architectural choices for the integration, termed as tightly-coupled and loosely-coupled interworking, has been described. The WLANs when compared to 3G networks have high-speed data rates but small coverage area. The WLANs infrastructure is expensive compared to wireline LANs but cheaper when compared to 3G infrastructure.

References

C. Perkins (Editor). IP Mobility Support for IPv4. RFC 3220, IETF, January 2002.

http://www.nationmaster.com/encyclopedia/1G, Accessed 1st January, 2009.

Hazysztof Wesolowshi, Mobile Communication System, John Wiley & Sons, 2002

J.H.Schiller, Mobile Communications, Addison-Wesley, Reading Mass, 2000

M. Buddhikot, G. Chandranmenon, S. Han, Y. W. Lee, S. Miller, L. Salgarelli, Integration of 802.11 and Third-Generation Wireless Data Networks, IEEE INFOCOM 2003.

Removable User Identity Module Standard for CDMA 2000 Spread spectrum Systems. C.S0023-0, 3GPP2, June 2000.

The Wireless Telecommunications Market in Japan, April 2006, Market Research Centre, Canada

Wireless IP Network Standard. P.S0001-A-1, Third Generation Partnership Program 2 (3GPP2), 2000

About the Author

Done my master's in telecommunication. Worked as a project engineer in Transcell Technical Services, India. Want to research on RF technologies to find its affect on the environment.

4 Channel wireless trigger for strobe light, mono light - CowboyStudio.com

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