The Global Positioning System through time: the history of GPS

Blaise Mibeck

On May 7, 2009, the United States Government Accountability
Office (GAO) reported on the future of the Global Positioning
System (GPS). To put it lightly, the future does not look good.
At issue is the real possibility that “in 2010, as old
satellites begin to fail, the overall GPS constellation will
fall below the number of satellites required to provide the
level of GPS service that the U.S. government commits to.”

How did we get to this point? Most users of GPS are aware that
many satellites overhead provide the signals they use to map
their position or track their progress across town. How many
users know were GPS came from?

The first GPS was invented in 1610 by Galileo. It involved a
telescope and a table of eclipse times for Jupiter's moons.
Measuring the altitude of Polaris gave your latitude. By using
the eclipsing of Jupiter's moons as “ticks” from a global clock,
the time at home base could be determined (using the book of
tables). Comparing local time with the time at home base
produced longitude, or how far east or west you have gone.

Sure, it seems strange to refer to this as the first Global
Positioning System, but in principle today's GPS and that of
Galileo are identical. Each has a ground segment, a space
segment and a user. Each depends on time for the determination
of distance or location. More importantly, the initial
application was identical: navigation at sea. Galileo's GPS was
submitted to a challenge set by King Philip II of Spain in 1598.
Philip wanted a method for determining longitude (latitude was
easy) in order to reduce the risk of shipping goods from the New
World. It wasn't until 1761 that John Harrison's marine
chronometer became the first practical method for determining
longitude at sea.

Even with John Harrison's clock, the problem of position
determination persisted. This problem has always been highly
important to conducting war. The strategic implication of
knowing your position is multifaceted. Global positioning
affects the principles of warfare that deal with deployment of
mass, economy of force, maneuverability, unity of command,
surprise and simplicity. More important to land warfare is the
challenge of knowing your position despite Fog of War (FOW). FOW
describes the effect of battle field chaos that results in
disorganization, loss of central command and casualties due to
“friendly fire”. Naval warfare has its own FOW to contend with,
but also requires constant attention to one's location due to
the featureless nature of the ocean.

Radionavigation, developed in the 1920's, begins to resemble
today's GPS. Shore-based transmitters and radio direction
equipment aboard ships or planes made up this system. Two or
more stations were required for the navigator to triangulate his
position. This only worked in two dimensions (latitude and
longitude) and also encountered problems during bad weather.

Galileo's method, Harrison's clock and shoreline radio
transmitters represent the incremental advances needed to make
modern GPS. These inventions were motivated by trade and used
for conducting war.

To understand GPS today – to get the big picture – it is
important to realize that the problem it solves is ancient. By
seeing the important role global positioning has always played
in trade and war, today's user can better appreciate the system
they take for granted and the politics involved in its use.

How to Find the Best GPS System for Your Car

Mike Hamilton

There are many great GPS devices out there, but how do you
determine which is the best for use in your car? Of the major
brands there is Tom Tom, Magellan, and Garmin.

All of the major brands have something that you will or may find
useful or "cool". The trick is to find a GPS unit that does what
you need and has the most features that are useful to you. For
instance if you have an IPod ready sound system for your car
than a GPS system that plays MP3s is probably not a big deal and
you will, more than likely not want to pay extra for it.

One feature that you will want to be absolutely certain that
your GPS system has if you are going use it while driving is
menu simplicity. The last thing you want while motoring down the
road is to have to navigate a complex menu or the touch screen
is too difficult to hit just right to do just what you want.

The other major item to be on the lookout for is readability.
Some type of anti-glare screen is a must. You don't want to be
in urban traffic during rush hour and have a screen that is
absolutely worthless.

One other thing to check on is does the GPS system come with all
you need to make it work. If other accessories that you want or
need are not included you will want to price them before
purchasing the GPS system and it is too late. Some things that
may fall into this category are the mount and the power cord.
Some units come with a USB cord to charge it up with your
computer but not a cigarette lighter or AC cord.

A Personal GPS Locator Can Make Your Life Easier

John Taylor

A personal GPS locator is a handy little unit taking advantage
of assisted GPS technology for helping to determine its own
location as precise and reliable as possible. The location
information is normally triggered by requests from the internet
or from cell phones.

If you're making the request from the internet, you need to go
to a certain URL that the GPS locator vendor gives you and log
in. Then you will have to follow the instructions with normally
is nothing more that pushing a button or make a click on your
mouse and the real time location of you and your GPS locator
unit will be displayed on a map. You will be able to see your
neighborhood on this map and zoom it in and out and also scroll
it in the directions you want.

Using the cell phone alternative all you have to do is sending a
text-message to a number that your personal GPS locator's vendor
gives you will get the same as described above displayed on your
cell phone window.

Some of the GPS locator units offer personalized safety Zones.
What do I mean by this? A safety zone is a customized virtual
boundary around the location that you've chosen. For equipment
with this function you can normally be alerted via email and/or
text message when you enter or leave any safety zone you have
defined. Most GPS locator units allow you to create several such
zones and they can all be active simultaneously at any given
time.

Continuous Tracking

Dependent of what type of GPS locator you have you can set how
often the feature shall update your location, for example every
5 minutes or every 10 minutes, etc. The last updated time will
normally be displayed on the map or another place.

History of Locations

Location history can be useful; therefore many models are
equipped with this feature. The more expensive the model the
more detailed information you normally get. With this feature
you will have an overview of stored information so you can see
where your GPS locator has moved in a certain periode of time,
for example the past hour, day, week or even month. Models with
this feature will often display the information on a map, that
you are able manipulate as the real-time map, such as zooming
and scrolling.

Power Alerts

Depending on the model of your personal GPS locator, you can be
notified through email or text message when your GPS unit has
been powered off or when the battery's capacity level is at a
certain level, for example when there is 20 percent battery
power left.

As you may already know personal GPS locators are in the same
class as cell phones and other electronic communication devices
when it comes to aviation security, which means you can't use
them on airplanes.

Why A GPS Facilitated Vehicle Tracking Mechanism Can Ensure Peace Of Mind

John Mahoney

If you are part of a logistics or supply chain network then you
probably need a vehicle tracking system in place. This will
improve on your productivity and ensure peace of mind. Safety in
emergencies One of the best things about a vehicle tracking
mechanism is that you can ensure increased safety for both
yourself and your family members.

There is a special button installed in such GPS enabled systems
that you can press during emergencies. Whether it is a situation
of carjacking or some other issue, the respective operator of
the carrier can assist you. Even in situations where it maybe
harmful to talk to you directly, the operator can contact law
enforcement authorities on your behalf.

Help when stranded Our vehicles let us down when we least expect
it. If your vehicle is down and out because of some mechanical
issue then you just need to press a button and help will be at
hand. This is another beneficial aspect of vehicle tracking
systems.

This button is typically known as the ‘communication’ button
with almost all carriers. Being locked out If your kids have
locked you outside the vehicle, you can still be assured with a
vehicle tracking mechanism. All you need to do is contact the
call center of this carrier. Then the vehicle can be unlocked
easily. Losing your vehicle Lost sight of your vehicle? No
problem. With a vehicle tracking system, you can dial in to the
call center.

The operator will help to locate your vehicle and lights will
begin flashing on the vehicle. The horn will start honking too.
Thus, if you are lost in a crowded marketplace and need help
finding your vehicle, a vehicle tracking mechanism can be like a
virtual Godsend.

These operators will then locate your stolen vehicle and note
down the speed at the time of theft. They can then contact law
enforcement and police officials to recover the vehicle.
Logistics and tracking issues If you are part of the supply
chain and logistics segment then a vehicle tracking mechanism
can prove invaluable to you. Having such a system installed can
help you efficiently track movement of vehicles and
equipment.

Thus, you will know exactly how soon your vehicles will reach
their destination, thereby infusing more predictability into
your workflow. In addition, you can pinpoint any slackness on
the part of your employees by efficient tracking methods
introduced by a vehicle tracking installation. Better customer
service scores With the installation of a vehicle tracking
mechanism, you can up your customer satisfaction scores. Through
efficient tracking methods, you can guarantee fast shipping to
your customers – and live up to your promise. This will ensure
repeat sales for your business and more satisfied customers as
well.

IEEE 802.16: Broadband Wireless MAN Standard (WiMAX)

IEEE 802.16: Broadband Wireless MAN Standard (WiMAX)


An 802.16 wireless service provides a communications path between a subscriber site and a core network such as the public telephone network and the Internet. This wireless broadband access standard provides the missing link for the "last mile" connection in metropolitan area networks where DSL, Cable and other broadband access methods are not available or too expensive. The Wireless MAN technology is also branded as WiMAX.

IEEE 802.16 standards are concerned with the air interface between a subscriber's transceiver station and a base transceiver station. IEEE 802.16 is approved by th IEEE in June 2004. Three working groups have been chartered to produce standards: Task Group 1 of IEEE 802.16 developed a point-to-multipoint broadband wireless access standard for systems in the frequency range 10-66 GHz. The standard covers both the Media Access Control (MAC) and the physical (PHY) layers. Task groups a and b are jointly producing an amendment to extend the specification to cover both the licensed and unlicensed bands in the 2-11 GHz range.

IEEE 802.16 and WiMAX are designed as a complimentary technology to Wi-Fi and Bluetooth. The following table provides a quick comparison of 802.16a with to 802.11b:

Parameters	802.16a (WiMAX)	802.11 (WLAN)	802.15 (Bluetooth)
Frequency Band	2-11GHz	2.4GHz	Varies
Range	~31 miles	~100 meters	~10meters
Data transfer rate	70 Mbps	11 Mbps 55 Mbps	20Kbps 55 Mbps
Number of users	Thousands	Dozens	Dozens

WPAN: Wireless Personal Area Network Communication Technologies

Wireless Personal-Area Network (WPAN) is a personal area network using wireless connections. WPAN is used for communication among devices such as telephones, computer and its accessories, as well as personal digital assistants, within a short range.

The reach of a PAN is typically within 10 meters. Technologies enabling WPAN include Bluetooth, ZigBee, Ultra-wideband(UWB), IrDA, HomeRF, etc., in which the Bluetooth is the most widely used technology for the WPAN communication.

Each technology is optimized for specific usage, applications, or domains. Although in some respects, certain technologies might be viewed as competing in the WPAN space, but they are often complementary to each other.

The IEEE 802.15 Working Groups is the organization to define the WPAN technologies. In addition to the 802.15.1 based on the Bluetooth technology, IEEE proposed two additional categories of WPAN in 802.15: the low rate 802.15.4 (TG4, also known as ZigBee) and the high rate 802.15.3 (TG3, also known as Ultra-wideband or UWB). The TG4 ZigBee provides data speeds of 20 Kbps or 250 Kbps, for home control type of low power and low cost solutions. The TG3 UWB supports data speeds ranging from 20 Mbps to 1Gbps, for multi-media applications.

In the following table, the main characters of the WPAN technologies as specified in the IEEE 802.15 are compared:

Parameters	Bluetooth (IEEE 802.15.1)	UWB (IEEE 802.15.3)	ZigBee (IEEE 802.15.4)
Applications	Computer and accessory devices Computer to compute Computer with other digital devices	Multimedia content transfer, High-resolution radar, Ground-penetrating radar, Wireless sensor network, Radio locations systems	Home control Building automation Industrial automation Home security Medical monitoring
Frequency Band:	2.4 - 2.48GHz	3.1-10.6GHz	868MHz 902-928MHz 2.4-2.48GHZ
Range	~10 meters	~10 meters	~100 meters
Maximum Data transfer rate:	3 Mbps	1 Gbps	20 Kbps 40 Kbps 250 Kbps
Modulation	GFSK, 2PSK, DQSP, 8PSK	OPSK, BPSK	BPSK (868/928MHz) OPSK (2.4GHz)

WPAN, WLAN and WMAN technologies are complementary to each other and each play a unique role in today’s wireless communications. The following table outlines the three technologies:

Parameters	WMAN (IEEE 802.16 WiMAX)	WLAN (IEEE802.11)	WPAN (IEEE802.15)
Frequency Band:	2-66GHz	2.4 -5.8GHz	868 -10.6GHz
Range	~31 miles	~100 meters	~10meters (Bluetooth and UWB) ~100 meters (ZigBee)
Maximum data transfer rate:	134 Mbps	55 Mbps	1Gbps
Number of users:	Thousands	Dozens	Dozens

Comparison of WLAN, WPAN and WMAN Technologies

There are three main wireless technology groups for the fixed wireless communications, namely, Wireless LAN (or Wi-Fi), Wireless Personal Area Networking (WPAN) and Wireless Metropolitan Area Networking (or WiMax). While competing in many applications, each technology has its own application focus and limitations.

The key parameters of WLAN, WPAN and WMAN(WiMax) technologies are compared and displayed in the table below:

Technology	WLAN (IEEE)
Standard	802.11 Legacy	802.11a	802.11b	802.11g	802.11n
Release year	1997	1999	1999	2003	2008
Frequency Band	2.4GHz	5.8GHz	2.4GHz	2.4GHz	2.4 – 5.8GHz
Maximum Range	~70 meters	~100 meters	~100 meters	~110 meters	~160 meters
Maximum data rate	2Mbps	54Mbps	11Mbps	54Mbps	248Mbps
Number of users	Dozens	Dozens	Dozens	Dozens	Dozens
Access Method	DSSS, FHSS	OFDM	DSSS, CCK	OFDM	MIMO
Modulation Method	GFSK, BPSK, DBPSK, DQPSK	BPSK, QPSK, 16-QAM, 64-QAM	DPSK, DBPSK, DQPSK	BPSK, QPSK, 16-QAM, 64-QAM and DBPSK, DQPSK	BPSK, QPSK, 16-QAM, 64-QAM

Technology	WPAN (IEEE)				WMAN WiMAX (IEEE)
Standard	802.15.1 (Bluetooth)	802.15.3 (UWB)	802.15.3a (WiMedia)	ZigBee 802.15.4-2003 802.15.4-2006	802.16-2004 (802.116d) 802.16e-2005 (802.16e)
Release year	2002	2003	*	2003 and 2006	2004 and 2005
Frequency Band	2.4Ghz	3.1 to 10.6 GHz	2.4GHz	868 MHz, 915 MHz, 2.4 GHz	2-66GHz
Maximum Range	~10meters	~10meters	~10meters	~100 meters	~50 km
Maximum data rate	3Mbps	55Mbps – 1Gbps	110Mbps – 1Gbps	250 Kbps	134 Mbps
Number of users	Dozens	Dozens	Dozens	Dozens	Thousands
Access Method	FHSS	DS-UWB, OFDM	MB-OFDM	DSSS	MIMO-SOFDMA
Modulation Method	GFSK, 2PSK, DQSP, 8PSK	OPSK, BPSK, OOK, PAM, PPM, Bi-Phase	QPSK, DCM	BPSK (868/928MHz) OPSK (2.4GHz)	QPSK, QAM

3GPP IP Multimedia Subsystem (IMS) Architecture

The IP Multimedia Subsystem (IMS) is an architectural framework defined by the wireless standards body 3rd Generation Partnership Project (3GPP) for delivering IP multimedia services to mobile users based on the UTMS network. A similar system called Multimedia Domain (MMD) was defined by the 3GPP2 (a different organization) for the CDMA2000 network, which was based on the 3GPP IMS.

For the network access, the user can connect to an IMS network in various ways using IP. Direct IMS terminals (such as mobile phones, personal digital assistants (PDAs) and computers) can register directly on an IMS network, even when they are roaming in another network or country (the visited network). The only requirement is that they can use IPv6 (also IPv4 in early IMS) and run Session Initiation Protocol (SIP) user agents. Fixed access (e.g., Digital Subscriber Line (DSL), cable modems, Ethernet), mobile access (e.g. W-CDMA, CDMA2000, GSM, GPRS) and wireless access (e.g. WLAN, WiMAX) are all supported. Other phone systems like plain old telephone service (POTS -- the old analogue telephones), H.323 and non IMS-compatible VoIP systems, are supported through gateways.

The IP Multimedia Core Network Subsystem is a collection of different functions, linked by standardized interfaces, which grouped form one IMS administrative network. The key functions of the core network are:

Home Subscriber Server (HSS), or User Profile Server Function (UPSF), is a master user database that supports the IMS network entities that actually handle calls. It contains the subscription-related information (user profiles), performs authentication and authorization of the user, and can provide information about the user's physical location.

Call Session Control Function (CSCF) is used to process SIP signaling packets in the IMS. There are three types of CSCF: Proxy-CSCF (P-CSCF), Serving-CSCF (S-CSCF) and Interrogating-CSCF (I-CSCF).

Application servers (AS) host and execute services, and interface with the S-CSCF using SIP.

MRF (Media Resource Function) provides media related functions such as media manipulation (e.g. voice stream mixing) and playing of tones and announcements.

A BGCF (Breakout Gateway Control Function) is a SIP server that includes routing functionality based on telephone numbers.

Media Resources are those components that operate on the media plane and are under the control of IMS Core functions. Specifically, Media Server (MS) and Media gateway (MGW).

CDMA2000: 3G Standard Based on CDMA IS-95

CDMA2000 is the 3rd Generation solution based on CDMA IS-95, which supports 3G services as defined by the ITU 3G standards IMT-2000. CDMA2000 defines both an air interface and a core network. Cdma2000 has already been implemented to several networks as an evolutionary step from cdmaOne as cdma2000 provides full backward compatibility with IS-95B.

The CDMA2000 standard is evolving to continually support new services in a standard 1.25 MHz carrier. The first phase of CDMA2000, or CDMA2000 1X will deliver average data rates of 144 kbps. Phase two, labeled CDMA2000 1xEV, will provide for data rates greater than 2Mbps.

CDMA2000 1X (or the IS-2000 standard) published by the Telecommunications Industry Association (TIA), offers average data rates of 144 kbps, backward compatibility with cdmaOne networks, and many other performance improvements. CDMA2000 1X can be implemented in existing cdmaOne spectrum (1.25 MHz) or in new spectrum allocations. A CDMA2000 1X network will support simultaneous voice and data services with low latency and improved performance.

The evolution of CDMA2000 beyond 1X is called CDMA2000 1xEV. 1xEV is divided into two steps: 1xEV-DO and 1xEV-DV. 1xEV-DO stands for 1X Evolution Data Only. 1xEV-DV stands for 1X Evolution Data and Voice. Again CDMA2000 1XEV can be implemented in existing cdmaOne spectrum (1.25 MHz) or in new spectrum allocations.

1xEV-DO, requiring a separate carrier for data, will provide for higher data rates on 1X systems. By allocating a separate carrier for data, operators will be able to deliver peak data rates in excess of 2 Mbps at its best effort. 1xEV-DV allows data and voice services for CDMA2000 in one carrier. A 1xEV-DV carrier will provide not only high speed data and voice simultaneously, but will also be capable of delivering real-time packet services.

The standards for a CDMA packet core network are being developed by the TR45.6 working group of the TIA. These standards are being developed by using existing standards from the IETF (Internet Engineering Task Force) on Mobile IP. 3GPP2 is also busy defining the evolution of a CDMA2000 network to All-IP. The CDMA2000 PCN will be the first step in this evolution.

CDMA2000 Mobile Wireless Network Architecture

CDMA2000 is a hybrid 2.5G / 3G technology of mobile telecommunications that use CDMA (code division multiple access) to send digital radio, voice, data, and signaling data between mobile phones and cell sites. CDMA2000 is standardized by the 3rd Generation Partnership Project 2 (3GPP2).

The cdma2000 network comprises three major parts: the core network (CN), the radio access network (RAN) and the mobile station (MS). The core network is further decomposed in two parts, one interfacing to external networks such as the Public Switched Telephone Network (PSTN) and the other interfacing to the IP based network such as Internet. The mobile station terminates the radio path on the user side of the network and enables subscribers to access network services over the Um interface.

In a CDMA2000 access network, two radio access network technologies are supported: 1xRTT and EV-DO. CDMA2000 is considered a 2.5G (or 2.75G) technology when the 1xRTT access network is used and a 3G technology when the EV-DO access network is used.

CDMA2000 1xRTT, the core CDMA2000 wireless air interface standard, is also known as 1x, 1xRTT, and IS-2000. The designation "1x", meaning "1 times Radio Transmission Technology", indicates the same RF bandwidth as IS-95 (CDMA-One): a duplex pair of 1.25 MHz radio channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to the original set of 64. Although capable of higher data rates, most deployments are limited to a peak of 144 kbit/s. IS-2000 also made changes to the data link layer for the greater use of data services, including medium and link access control protocols and QoS.

CDMA2000 EV-DO (Evolution-Data Optimized or Evolution-Data only), a broadband access radio technology standardized by 3rd Generation Partnership Project 2 (3GPP2), provides access to mobile devices with air interface speeds of up to 2.4 Mbit/s with Rev. 0 and up to 3.1 Mbit/s with Rev. A. The industry is working newer generations of EV-DO such as Rev. B and Rev. C, etc.

The CDMA2000 access network may perform mobility management functions for registering, authorizing, authenticating and paging IP based terminals, independent of circuit based terminals. The access network may perform handoffs within an access network and between access networks of the same technology and may support handoffs between access networks of differing technologies.

The key components of the cdma2000 access network are:
Base Transceiver System (BTS): an entity that provides transmission capabilities across the Um reference point. The BTS consists of radio devices, antenna and equipment.

Base Station Controller (BSC): an entity that provides control and management for one or more BTSs.

Packet Control Function (PCF): an entity that provides interface function between the access network and the packet switched network.

UMTS: Universal Mobile Telecommunications System

Universal Mobile Telecommunications System (UMTS) is a key 3G mobile technology identified by the ITU. UMTS is the natural evolutionary choice for operators of GSM networks, a 2G mobile network. Using fresh radio spectrum to support increased numbers of customers in line with industry forecasts of demand for data services over the next decade and beyond, "UMTS" is synonymous with a choice of WCDMA radio access technology that has already been selected by approaching 120 licensees worldwide.

A UMTS network consist of three interacting domains; Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions. The following is a list of key UMTS components:

• UMTS systems (including satellite)

• PublicLandMobile Network (PLMN)
• MSC/VLR or SGSN
• Location Area
• Routing Area (PS domain)
• UTRAN Registration Area (PS domain)
• Cell
• Sub cell

UMTS system uses the same core network as the GPRS and uses entirely new radio interface. The core network provides the switching, routing, transport, and database functions for user traffic. The core network contains circuit-switched elements such as the MSC, VLR, and gateway MSC (GMSC). It also contains the packet-switched elements SGSN and GGSN. The EIR, HLR, and AuC support both circuit- and packet-switched data. The Asynchronous Transfer Mode (ATM) is the data transmission method used within the UMTS core network.

The new radio network in UMTS is called UTRAN (UMTS Terrestrial Radio Access Network) and is connected to the core network (CN) of GPRS via Iu interface. The Iu is the UTRAN interface between the Radio network controller RNC and CN.

CDMA: Code Division Multiple Access

Code Division Multiple Access (CDMA) is a cellular technology defined by Qualcomm in IS-95 and IS-2000.Other widely used multiple access techniques for cellular are Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA).

CDMA is a form of Direct Sequence Spread Spectrum communications. In general, Spread Spectrum communications is distinguished by three key elements: 1) The signal occupies a bandwidth much greater than that which is necessary to send the information, which results in immunity to interference and jamming and multi-user access; 2) The bandwidth is spread by means of a code which is independent of the data; 3) The receiver synchronizes to the code to recover the data. The use of an independent code and synchronous reception allows multiple users to access the same frequency band at the same time.

Due to increasing market demand for a convered network for both voice and data cpmmunications, CDMA technologies are evolving into CDMA2000 to meet the challenges. CDMA2000 is the 3rd Generation solution based on IS-95. Unlike some 3G standards, It is an evolution of an existing CDMA wireless standard. CDMA2000 supports 3G services as defined by the International Telecommunications Union (ITU) for IMT-2000. The goal is access to any service, anywhere, anytime from one terminal - true converged, mobile services.

The term Code Division Multiple Access (CDMA) is also widely used to refer to a key technology in the Universal Mobile Telecommunications System (UMTS). The two different uses of this term can be confusing. Actually, the Qualcomm standard CDMA and UMTS have been competing for adoption in many markets.

GSM/GPRS/UMTS Mobile Wireless Network Evolution

n the past decades, the mobile wireless network has migrated from the first generation (1G) to the third generation (3G), and 4G is in the time table. As one of the technology branches in the mobile wireless communication, the GSM has been upgraded to GPRS, and then UMTS. The road map of the GSM/UMTS network evolution is charged by the Third Generation Partnership Project (3GPP).

The GSM/GPRS/UMTS network evolution contains not only technical evolution but also expansion to network architecture and services.

• Technical evolution: how network elements are developed and with which technology.
• Network evolution: in result of network element evolutions the general architecture and functionality of the network is changing.
• Service evolution: demand generated by the end-users that can be supported by the technical features of the network.

	GSM	GPRS	UMTS
Network Elements	Mobile station (MS) Base transceiver station (BTS) Base station controller (BSC) Base station subsystem (BSS) Mobile switching center (MSC) Authentication center (AuC) Home location register (HLR) Visitor location register (VLR)	Terminal Equipment (TE)Base transceiver site (BTS) Base Station Controller (BSC) GPRS Support Nodes (GSNs) Serving GPRS support node (SGSN) Gateway GPRS support node (GGSN)	Radio Network Controller (RNC)Node BUMTS User EquipmentPlus GPRS components
Network Functions	Circuit Switched Voice/DataNarrow band access	Circuit Switched Voice Packet Switched data Narrow band access	Packet switch for voice and dataIP multimedia subsystem (IMS)Broadband access using UTRAN
Services	Voice	VoiceShort messagesLow speed data	VoiceMessagesHigh speed dataMultimedia

Radio Access Network (RAN) Standards for 3G UMTS and CDMA2000 Networks

A radio access network (RAN) refers to the network that sits between the mobile phones, and the core network (CN). Both UMTS and CDMA2000 networks have their own radio access network air interface definitions. RAN provides radio bearers between the core network and the mobile station for the transport of user data and non-access stream signaling, thus enabling mobile stations to access the service offered by the PSTN and Internet. The main RAN function includes establishment, maintenance, and termination of radio channels; radio resource management; and mobility management. The RAN consists of the base station (BS) and packet control function (PCF). The base station is further decomposed in one control and one or multiple radio-terminating equipment portions named base station controller (BSC) and base transceiver station (BTS), respectively.

W-CDMA (Wideband Code Division Multiple Access) is the first 3G air interface for the UMTS technologies, a third generation follow-on to the 2G GSM networks deployed worldwide. W-CDMA can be implemented by migrating via GPRS and EDGE on the 2G network infrastructure of the GSM standard that is used in Europe and worldwide. W-CDMA allows transmission of signals for various services with variable data rates on 5 MHz bandwidths. Key features of WCDMA are cited below:

• Radio channels are 5MHz wide.
• Chip rate of 3.84 Mcps
• Supports two basic modes of duplex, frequency division and time division. Current systems use frequency division, one frequency for uplink and one for downlink. For time division, FOMA uses sixteen slots per radio frame, where as UMTS uses 15 slots per radio frame.
• Employs coherent detection on uplink and downlink based on the use of pilot symbols.
• Supports inter-cell asynchronous operation.
• Variable mission on a 10 ms frame basis.
• Multicode transmission.
• Adaptive power control based on SIR (Signal-to-Interference Ratio).
• Multiuser detection and smart antennas can be used to increase capacity and coverage.
• Multiple types of handoff between different cells including soft handoff, softer handoff and hard handoff.

New air interface technologies such as HSPA and HSPA+ are defined for the UMTS systems with better performance and functionalities.

On the other hand, CDMA2000 covers a family of mobile communication technologies that further develop the 2G mode CDMAOne, whose use is restricted to the USA, South America, Korea and Japan. CDMA2000 3G network, uses its own radio access network technologies. The CDMA2000 standards CDMA2000 1xRTT, CDMA2000 EV-DO, and CDMA2000 EV-DV are approved radio interfaces for the ITU's IMT-2000 standard and a direct successor to 2G CDMA, IS-95 (cdmaOne). CDMA2000 is standardized by 3GPP2. CDMA2000 is designed to use transmission bandwidth of 1.25 MHz.

UMTS/WCDMA Logical, Transport and Physical Channels

WCDMA is the main air interface standard for the 3G UMTS mobile network. The mobile station and base station communicate by means of several physical channels that are transmitted on a given frequency assignment. The "Downlink" refers to a radio link for the transmission of signals from the base station to a UE (mobile station) while the "Uplink" refers to a radio link for the transmission of signals from a UE (mobile station) to the base station.

There are three types of channels in the WCDMA technologies: Physical Channel, Transport Channel and Logical channel. The Transport Channels are interface between MAC and Layer 1, while Logical Channels are interface between MAC and RLC. The logical and transport channels define WHAT data are transported, while the physical channels define HOW and with what physical characteristic the data are transport.

Transport channels can be further subdivided into Common Transport Channels; and dedicated transport channels. Common transport channel types are:

• Random Access Channel (RACH): A contention based uplink channel used for transmission of relatively small amounts of data, e.g. for initial access or non-real-time dedicated control or traffic data.
• Common Packet Channel (CPCH): A contention based channel used for transmission of bursty data traffic. This channel only exists in FDD mode and only in the uplink direction. The common packet channel is shared by the UEs in a cell and therefore, it is a common resource. The CPCH is fast power controlled.
• Forward Access Channel (FACH): Common downlink channel without closed-loop power control used for transmission of relatively small amount of data.
• Downlink Shared Channel (DSCH): A downlink channel shared by several UEs carrying dedicated control or traffic data.
• Uplink Shared Channel (USCH): An uplink channel shared by several UEs carrying dedicated control or traffic data, used in TDD mode only.
• Broadcast Channel (BCH): A downlink channel used for broadcast of system information into an entire cell.
• Paging Channel (PCH): A downlink channel used for broadcast of control information into an entire cell allowing efficient UE sleep mode procedures. Currently identified information types are paging and notification. Another use could be UTRAN notification of change of BCCH information.
• High Speed Downlink Shared Channel (HS-DSCH): A downlink channel shared between UEs by allocation of individual codes, from a common pool of codes assigned for the channel.

Dedicated transport channel types are:

• Dedicated Channel (DCH): A channel dedicated to one UE used in uplink or downlink.
• A general classification of logical channels is into two groups; Control Channels (for the transfer of control plane information) and Traffic Channels (for the transfer of user plane information).

Control Channels:

• Broadcast Control Channel (BCCH): A downlink channel for broadcasting system control information.
• Paging Control Channel (PCCH): A downlink channel that transfers paging information. This channel is used when the network does not know the location cell of the UE, or, the UE is in the cell connected state (utilising UE sleep mode procedures).
• Common Control Channel (CCCH): Bi-directional channel for transmitting control information between network and UEs. This channel is commonly used by the UEs having no RRC connection with the network and by the UEs using common transport channels when accessing a new cell after cell reselection.
• Dedicated Control Channel (DCCH): A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is established through RRC connection setup procedure.
• Shared Channel Control Channel (SHCCH): Bi-directional channel that transmits control information for uplink and downlink shared channels between network and UEs. This channel is for TDD only.

Traffic Channels:

• Dedicated Traffic Channel (DTCH): A Dedicated Traffic Channel (DTCH) is a point-to-point channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both uplink and downlink.
• Common Traffic Channel (CTCH): A point-to-multipoint unidirectional channel for transfer of dedicated user information for all or a group of specified UEs.

UMTS Network Interfaces and Protocol Stack

UMTS network follows the typical communication model in telecom which defines a set of horizontal and vertical layers. The horizontal layers are physical, network, transport and application layers – as defined in the OSI model. The vertical layers are functional areas, namely control plane, user plane and data plane. Control planes are used to control a link or a connection; user planes are used to transparently transmit user data from the higher layers. The UMTS network interfaces and protocol stacks follow the same communication model. Standard transmission issues, which are independent of UTRAN requirements, are applied in the horizontal transport network layer. The UTRAN requirements are addressed in the horizontal radio network layer across different types of control and user planes. The UMTS network introduces four new key interfaces and protocol stacks: Uu, Iub, Iur, and Iu.

Iu: Radio Access Network Application Part (RANAP) [3G TS 25.413]. This interface provides UTRAN–specific signaling and control over the Iu. The following is some typical RANAP functions:

• Overall radio access bearer (RAB) management, which includes the RAB’s setup, maintenance, and release
• Management of Iu connections
• Transport of nonaccess stratum (NAS) information between the UE and the CN; for example, NAS contains the mobility management signaling and broadcast information.
• Exchanging UE location information between the RNC and CN
• Paging requests from the CN to the UE
• Overload and general error situation handling

Iur: Radio Network Sublayer Application Part (RNSAP) [3G TS 25.423]. This interface provides UTRAN–specific signaling and control for the following sample functions:

• Management of radio links, physical links, and common transport channel resources
• Paging
• SRNC relocation
• Measurements of dedicated resources

Iub: Node B Application Part (NBAP) [3G TS 25.433]. This interface provides UTRAN specific signaling and control for the following sample areas:

• Management of common channels, common resources, and radio links
• Configuration management, such as cell configuration management
• Measurement handling and control
• Synchronization (TDD)
• Reporting of error situations

Uu: Radio Resource Control (RRC) [3G TS 25.331]. This interface handles the control plane signaling over the Uu between the UE and the UTRAN. Some of the functions offered by the RRC

include the following areas:

• Broadcasting information
• Management of connections between the UE and the UTRAN, which include their establishment, maintenance, and release
• Management of the radio bearers, which include their establishment, maintenance, release, and the corresponding connection mobility
• Ciphering control
• Outer loop power control
• Message integrity protection
• Timing advance in the TDD mode
• UE measurement report evaluation
• Paging and notifying

UMTS 3G Mobile Wireless Network Architecture

Universal Mobile Telecommunications System (UMTS), standardized by the 3GPP, is the 3G mobile communication technology successor to GSM and GPRS. UMTS combines the W-CDMA, TD-CDMA, or TD-SCDMA air interfaces, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codecs.

W-CDMA is the most popular cellular mobile telephone variant of UMTS in use. UMTS, using W-CDMA, supports up to 14.0 Mbit/s data transfer rates in theory with High Speed Downlink Packet Access (HSDPA), although the performance in deployed networks could be much lower for both uplink and downlink connections.

A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GeRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GeRAN includes the three lowest layers of OSI model. The network layer (OSI 3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.

The UMTS standard is an extension of existing networks based on the GSM and GPRS technologies. In UMTS release 1, a new radio access network UMTS terrestrial radio access network (UTRAN) is introduced. UTRAN, the UMTS radio access network (RAN), is connected via the Iu to the GSM Phase 2+ core network (CN). The Iu is the UTRAN interface between the radio network controller (RNC) and CN; the UTRAN interface between RNC and the packet-switched domain of the CN (Iu–PS) is used for PS data and the UTRAN interface between RNC and the circuit-switched domain of the CN (Iu–CS) is used for CS data.

UTRAN is subdivided into individual radio network systems (RNSs), where each RNS is controlled by an RNC. The RNC is connected to a set of Node B elements, each of which can serve one or several cells. Two new network elements, namely RNC and Node B, are introduced in UTRAN.

The RNC enables autonomous radio resource management (RRM) by UTRAN. It performs the same functions as the GSM BSC, providing central control for the RNS elements (RNC and Node Bs).

Node B is the physical unit for radio transmission/reception with cells. Node B connects with the UE via the W–CDMA Uu radio interface and with the RNC via the Iub asynchronous transfer mode (ATM)–based interface. Node B is the ATM termination point.