0018-9162/04/$20.00 © 2004 IEEE September 2004 23

P E R S P E C T I V E S

P u b l i s h e d b y t h e I E E E C o m p u t e r S o c i e t y

Beyond 3G:CompoundWireless Services

A key feature of third-generation wireless systems is support forhigh bit-rate telecommunications. This technology, known ascode division multiple access, is being deployed in two versions.CDMA2000, for which the Telecommunications Industry Asso-ciation committee TR-45 developed a standard, supports up to

2.4 Mbps,1 while wideband CDMA, standardized by the EuropeanTelecommunications Standards Institute, supports up to 8 Mbps.2 Thesehigh bit rates are leading to a plethora of new wireless services3-5 that broadlyfall into three categories:

• information retrieval—for example, identify a user’s location, deter-mine a route to a store, obtain a weather forecast, download an inven-tory of spare parts while doing field repair;

• mobile commerce—for example, book a flight, pay a parking meter,authorize a credit card payment, order a part while doing field repair;and

• general communications—for example, place a phone call, check e-mail,activate an air conditioner at home, record a field repair result into anoffice log.

Although 3G services are still under development, researchers are alreadyexploring the architectural needs of next-generation wireless services.6

Compound wireless services will enable users to combine different types ofservices to carry out specialized, elaborate functions. (A pending patent pro-tects this concept and its methodology.) For example, transmitting still imagesfrom a cell phone is an appealing feature. However, combining this capa-bility with a home alarm warning system—so that, when activated, the sys-tem automatically dials the owner’s cell phone and transmits pictures fromstrategically located video cameras—would have considerably more value.

COMPOUND WIRELESS SERVICESA compound wireless service consists of a combination of component

wireless services in an executable sequence that a user can store in memoryand invoke in the future when desired. This can be

• a fundamental wireless service that cannot be partitioned into sepa-rately identifiable services—for example, identify a location, determine

Next-generationwireless services willenable users to carryout specialized,elaborate functions bycombining componentservices offered by various sources.

Thaddeus J.A. KobylarzIEEE Life Member

24 Computer

a travel route, obtain vehicular travel infor-mation, determine travel route delays, displaya short message, announce a short message,transmit/receive a still image;

• a utility service that carries out a function withina particular compound service sequence—forexample, invoke a compound service, determineif equality exists, determine if inequality exists,execute an event, execute a pause, assign avalue, evaluate a service constraint, display aconstant value, announce a constant value,carry out arithmetic operations; or

• another compound wireless service.

Compound wireless services could be built by a

• wireless service provider,• wireless subscriber/user,• wireless equipment supplier or manufacturer,• computer software supplier or manufacturer,

or • wireless third-party applications provider.

To demonstrate the utility of compound wirelessservices, consider having a severe time constraintfor driving a vehicle between two geographic points.This could apply, for example, to a commuter trav-eling between home and work, a cab or limousinedriver who must arrive at an airport in time for apassenger’s flight, or a charter bus driver who has toreach a tour destination in a timely manner. Threefundamental wireless services can be employed toachieve this vehicular route assistance:

• location service—determine the present loca-tion of a user’s wireless terminal in the vehicle;

• travel route computation—compute the leasttime-consuming drive between the currentwireless terminal location and a designateddestination; and

• traffic information retrieval—interrogate traf-fic information systems available from statepolice and other sources for travel routeregions.

The compound wireless service consists of con-tinual iterations of these three services, in the fol-lowing sequence, until the destination is reached:

1. Determine the present location and provide itto the wireless terminal. If the present locationis the same as the destination, inform the userand cease the iteration of services.

2. Compute the least time-consuming route fromthe present location to the designated destina-tion. If the route has changed, alert the user—orally, graphically, or textually—of a new routeand its directions.

3. Retrieve traffic information for the route’s regionsand determine if traffic delays, such as those dueto an accident, would ensue. If traffic delays existahead, repeat step 2 with the updated delay infor-mation; otherwise, proceed to step 1.

In this case, determining whether the present loca-tion is the destination (equality determination) anddeciding between repeating step 2 and going to step

Table 1. Vehicular route assistance service parameters.

Service Goal Functional expression

Location Determine geographical location of wireless terminal Location = Loc (WirelessTerminal#, Password)• WirelessTerminal# identifies terminal to be located• Password establishes permission to execute service

Routing Determine road route for driving between two points Route = Rte (Constraints, Location, Destination)• Constraints contains a list of restrictions, such as roads to avoid• Location is the route’s geographical origin• Destination is the route’s geographical end

Region bounding Determine permitted driving region containing route Region = Rgn (Route, Distance)• Route is the road route for driving between two points• Distance is the maximum additional driving distance

Traffic Determine traffic locations that may cause delays within a region Traffic = Trf (Region)• Region is the permitted driving region containing the route

Delays Determine delays ahead of location in route and region Delays = Dly (Route, Region, Location)• Route is the road route for driving between two points• Region is the permitted driving region containing the route• Location is the current wireless terminal geographical location

Route constraints Determine roads to avoid and use in region Constraints = Cns (Region, Criteria, Location)• Region is the permitted driving region containing the route• Criteria guide the constraint decisions—for example, traffic

delays or fastest route• Location is the current wireless terminal geographical location

1 (event-conditioned execution) represent utilityservices.

SERVICE PARAMETERSMost wireless services include parameters. A

compound wireless service builder has the optionto determine whether a given parameter is constantor variable. Table 1 lists the service parameters forthe vehicular route assistance service.

Some parameters also require initial values toexecute compound wireless services. These initial-ized parameters may also be constant, such asWirelessTerminal# and Destination, or variable,such as Constraints (which can assume an initialvalue of “none” or a long list of values).

Figure 1 is a flow chart of the vehicular routeassistance service. All potential parameter initial-izations are based on a value need for service exe-cution. Default assignments help avoid burdensomeinitializations—that is, parameters are alwaysassigned default values prior to compound wirelessservice invocation. Initialization overwrites defaultvalues for a specified subset of parameters at invo-cation. WirelessTerminal#, Password, Constraints,Distance, Wait, and Criteria can all use default val-ues and thereby avoid initialization.

The utility service Announce operates on theunderstood constant parameters “Delay ahead”and “At destination,” which require no initializa-tion. The Pse utility service reduces the frequencyof component wireless service invocations to onlythose necessary for satisfactory performance of thecompound wireless service. This lowers the cost ofusing the service, as does employing the short mes-sage service for data communication.

Functional expressions can be used to identify

compound as well as component services. If defaultvalues are used for the initialized parametersWirelessTerminal#, Password, Constraints, Dis-tance, Wait, and Criteria, a functional expressionfor the vehicular route assistance service would beTrip = Trp (Destination), where Destination is thegeographical end of a route.

As indicated earlier, compound wireless servicescan contain other compound wireless services. Toachieve this, it is necessary to build a compoundwireless service and then specify its functionalexpression in another compound wireless service.Figure 2 illustrates such recursion in the vehicularroute assistance service. The parameter Destination

September 2004 25

Destination = Address1

Trip = Trp (Destination)

Pause = Pse (Duration)

Destination = Address2

Trip = Trp (Destination)

Invoke

Initialized values• Address1 = “487 Route 56, Mayberry, TX, USA”• Address2 = “2010 Route 287, Wetlakes, OK, USA”• Duration = “10 hours”

Figure 2. Compoundwireless servicerecursion. The parameter Destination will firstassume the valueassigned toAddress1 and then,after a stopover ofsome duration,assume the valueassigned toAddress2.

Location = Loc (WirelessTerminal#, Password)

IsLocation =Destination

?

Announce (“At destination”)

Yes No

Route = Rte (Constraints, Location, Destination)

DoesRoute have a

Delay?

Invoke Initialized parameters• WirelessTerminal#• Password• Destination• Constraints• Distance• Wait• Criteria

No YesAnnounce (“Delay ahead”)

Traffic = Trf (Region)

Constraints = Cns (Region, Criteria, Location)

Region = Rgn (Route, Distance)

Delays = Dly (Route, Region, Location)

Pause = Pse (Wait)

Figure 1. Vehicularroute assistanceservice. The intialized parameters usedefault values andthereby avoidinitialization.

26 Computer

Toolbar

Drawing area

Services

Special capabilities

Location = Loc (WirelessTerminal#, Password)

Announce (Comment)

Route = Rte (Constraints, Location, Destination)

Invoke

IsA = B

?Yes No

Region = Rgn (Route, Distance)

Pause = Pse (Time)

Test Save Open Copy Paste Undo

A

Help

Help

Help

Help

Help

Help

Help

Please overwrite the following default choices, if desired:

Location =

Invoke

Location = Loc (WirelessTerminal#, Password)

“14 Green St., Maplewood, NJ, USA”

WirelessTerminal# = “1.973.433.1234”

Password = “Apples”

Please overwrite the following default choices, if desired:

A =

Invoke

Location = Loc (WirelessTerminal#, Password)

Location

“14 Green St., Maplewood, NJ, USA”B =

IsA = B

?Yes No

Announce (“At destination”) Pause = Pse (Time)

Display (“Time to leave home”)

Yes No

Initialized values

Invoke

Location = Loc (WirelessTerminal#, Password)

IsLocation = B

?

• WirelessTerminal# = “1.973.433.1234” • Password = “Apples”• B = “14 Green St., Maplewood, NJ, USA”• Time = “0.5 seconds”

(a)

(b)

(c)

Figure 3. GUI for building a compound wireless service. The figure shows interim steps (a and b) with initialization pop-up windows and (c) acompleted flow chart for the school bus location service.

will first assume the value assigned to Address1 andthen, after a stopover of some duration, assume thevalue assigned to Address2. The stopover durationneed not be precise, only sufficiently long to beginexecuting Trp before beginning the next route. Thepause is used merely to avoid needless service invo-cations during the stopover.

BUILDING COMPOUND WIRELESS SERVICESA cellular terminal or computer could be used to

build compound wireless services. A computer hasgreater computational power and thus more exten-sive building facilities. Consequently, a cellular ter-minal would likely be used to build less complexcompound wireless services or to modify servicesbuilt on a computer.

To illustrate the process involved in building acompound wireless service, consider the followingexample. Inclement weather can delay schoolbuses, causing children at stops along the route towait longer than usual. In areas prone to badweather, it would be useful to have a service thatperiodically determines a bus’s location andinforms parents when the bus is approaching astop, giving their children enough time to walkfrom home to the stop without unnecessarilyexposing them to the elements.

Figure 3 is a facsimile of a GUI that could be usedto build such a service. Menus contain textual andgraphical icons that represent component wirelessservices, appropriate word-processing tools, and spe-cial capabilities to facilitate building compound wire-less service. Users can click on these icons and dragselections into the drawing area to build a flow chart.

Each service icon has a help button to clarify selec-tions and, when appropriate, make suggestions viaa pop-up instruction window with menus. In addi-tion, when the user drags a selection to the drawingarea, a pop-up window appears with parameterdefault values and permitted override opportunities.If a service requires a choice from a repertoire of con-stants, a window shows these as well.

Figures 3a and 3b illustrate interim steps in build-ing the school bus compound wireless service withinitialization pop-up windows. Figure 3c shows thecompleted flow chart for the compound wirelessservice. The half-second pause represents the inter-val for sending short messages identifying the bus’slocation. After the user has finished building theservice, the system performs a test simulation toascertain correctness. The system then downloadsthe compound wireless service to a wireless termi-nal for future execution.

EXECUTING COMPONENT WIRELESS SERVICESFrom the standpoint of subscriber economy, the

wireless terminal should execute as many compo-nent services of a compound wireless service as pos-sible. Consider the following example. Attendeesat a periodic business meeting in a distant locationprefer to schedule flights home commensurate withthe scheduled conclusion, but the meeting has a his-tory of running late. It would therefore be helpfulto build a compound wireless service that, as a pre-caution, helps manage flight departure times in caseof an extended meeting.

Figure 4 shows the flow chart for such a service.The component wireless services are either com-

September 2004 27

AvailTime = BoardTime – GateTime

Display (“Missed flight”, AlternateFlightTable)

Yes No

GateTime = GtTm (CurrentTime, DriveTime, AirportTime)

Invoke

DriveTime = DrvTm (Location, Destination)

IsGateTime <BoardTime

?

Display (AlternateFlightTable) Display (“At ”, CurrentTime, “Available time is”, AvailTime)

Yes NoIs

AltrntFlghts= Yes

?

Display (“Available time = ”, AvailTime)

Initialized parameters• Location (meeting place) • Destination (airport)• BoardTime (one hour before flight time)• AlternateFlightTable (alternate flights downloaded by travel agent)

Figure 4. Flightdeparture time managementservice. With theexception of trafficinformation, thewireless terminalcould execute allcomponent services.

28 Computer

pound wireless services themselves or utility services.For example, the compound wireless DriveTime ser-vice determines the fastest route between the meet-ing place and the destination airport, consideringfactors such as traffic delays. It is similar to the vehic-ular route assistance service, although DriveTime iscomputed only once per invocation, and Locationand Destination are initialized constants. The ser-vice provider or third-party application providermust provide the traffic information, but the remain-ing component wireless services could be executedwithin the cellular terminal.

The compound wireless GateTime service is anarithmetic computation that utilizes the cellular ter-minal’s time clock, the computed DriveTime, andan initialized constant to estimate the AirportTimefor security, check-in, and so on. If the computedgate arrival time exceeds the scheduled boardingtime, the cellular terminal issues a warning that theuser will miss the flight and displays a table of alter-nate flights.

These three latter component wireless servicesdo not require cellular communication. TheAlternateFlightTable is a constant that the userdownloads with a travel agent’s assistance whenmaking travel reservations. It is also possible toacquire this table dynamically by building a com-ponent compound wireless service that communi-cates with the travel agency as needed during thecompound wireless service’s execution.

If the flight departure time management serviceestimates that the user will arrive at the gate priorto the scheduled boarding time (GateTime <BoardingTime), the service briefly displays the timedifference. Afterward, depending upon an initial-ized constant, it displays AlternateFlightTable or areminder of when this compound wireless servicewas executed and the available time at execution.Again, these component wireless services do notrequire any wireless communication.

C ompound wireless services could substan-tially increase the use of wireless telecom-munications, but they must meet certain

requirements to be successful. One such require-ment is the availability of easy-to-use compoundwireless service building tools; once the softwarefor such tools becomes available, third parties cansell it or wireless service providers can provide it aspart of subscription packages.

In addition, compound wireless services must beaffordable to the general public. For example, indi-vidual commuters, not just taxi and limousine com-panies, should be able to subscribe to a vehicularroute assistance service. Per-use rather than flat-rate pricing would more effectively expand the con-sumer base, stimulate building compound wirelessservices, and minimize costs. �

References1. R. Patty, “CDMA2000 1/spl times/EV-DO [for 3G

Communications],” IEEE Potentials, Oct./Nov.2002, pp. 10-13.

2. A.R. Karamchand Babu and Z.A. Abdul Rashid,“Performance Evaluation of Wideband CDMA AirInterface,” Proc. 2002 Student Conf. Research andDevelopment, IEEE Press, 2002, pp. 145-148.

3. M.W. Oliphant, “Third-Generation Wireless MustWait for Services to Catch Up,” IEEE Spectrum, June2002, pp. 14-16.

4. S.M. Cherry, “What’s Right with Telecom,” IEEESpectrum, Jan. 2003, pp. 30-34.

5. W. Webb, “From ‘Cellphone’ to ‘Remote Control onLife’: How Wireless Communications Will Changethe Way We Live Over the Next 20 Years,” Proc.2002 IEEE Radio Frequency Integrated Circuits(RFIC) Symp., IEEE Press, 2002, pp. 7-11.

6. S. Uskela, “Key Concepts for Evolution TowardBeyond 3G Networks,” IEEE Wireless Comm., Feb.2003, pp. 43-48.

Thaddeus J.A. Kobylarz is a consultant on wirelessservices and charging and billing for these services.He retired from Bell Laboratories in 2000 aftermore than 20 years of service as a telecommunica-tions system architect and has chaired numerouswireless standards committees. Kobylarz received aPhD in electrical engineering and computer sciencefrom North Carolina State University. He is a LifeMember of the IEEE. Contact him at t.kobylarz@ieee.org.

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