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`M CURRENTmuss SYSTIIS
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`The cellular digital packet data (CDPD) system is a widevarea wireless data service
`layed on the analog cellular telephone network. CDPD shares the FDMA voice ch:
`of the analog systems, since many of these channels are idle owing to the growth at
`tel cellular. The CDPD service provides packet data admission at rates of 19.2 k1);
`is available throughout the United States. However. since newer generations of celluls
`rents also provide data services and at higher data rates, CDPD is mostly being'replar
`these newerservicw. Thus, wide area wireless data services have not been very succt
`although emerging systems that offer broadband access may have more appeal.
`
`1.4.5 Broadband Wireless Access
`Broadband wireless access provides high-rate wireless communications between a his
`cess point and multiple terminals. These systems were initially proposedto support in
`rite video service loathe home, but the application emphasis then shilted to providing
`highaspeed data access (tens of Mbps) to the Internet and the World Wide Web as a
`high-speed data networks for homes and businesses.
`in the United States, two freq
`bands were set aside for these systems: part of the 28-682 spectrum for local distril
`systems (local mnltipoint distribution service, LMDS) and a band in the 2-Giiz ape
`for monopolitan distribution service (multichannel multipoint distribution services. Mlt
`LMDS represents a quick means for new service providers toeuter the already stifi' ct
`tition among wireless and wireline broadband service providers [5, Chap. 2.3]. MM
`a television and telecommunication delivery system with transmission ranges of 30-1
`[5, Chap. 11.11]. MMDS has the capability of delivering more than a hundred digital
`TV channels along with telephony and access to the Internet. MMDS will compete n
`with existing cable and satellite systems. Europe is developing sstandard similar to M
`called Hipersccess.
`WiMax is an emerging broadband wireless technology based on the [BEE 802.16 sin
`[16; 17]. The core 802.16 specification is a standard for broadband wireless access sy
`operating atradio frequencies between '2 Oil: and 11 Gliz for non-line-of-sight oper
`and between 10 Gllz and 6661312 for line-of-sight operation. Data rates of around 40
`will be available for fixed users and 15 Maps for mobile users. with a range of several
`meters. Many manufacmrers of laptops and PDAs (personal digital assistants) are pin
`to incorporate WiMsx once 'a becomes available to satisfy demand for constant intern
`(zest and email exchange from any location. WiMax will compete with wireless LAN
`cellular services. and possibly wireline services like cable and DSL (digital subscriber
`The ability of WiMax-‘to challenge or supplant these systems will dependron its rdativ
`formance and cost, which remain to be seen.
`
`1.4.6 Paging Systems
`Paging systems broadcast a short paging message simultaneously flout many tall but
`tions or satellites transmitting at very high power (hundreds of watts to kilowatts). 8y
`with terrestrial nansmitters are typically localized to aparticular geographic area. suc‘
`city or metropolitan region, while geosynchronons satellite transmitters provide nation
`international coverage. In both types of systems. no location management or routing
`tions are needed because the.paging message is broadcast over the entire coveragearea
`high complexity and power of the paging transmitters allows low-complexity, low-p
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`‘18
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`avertvraw or mucus: continuum
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`pocket paging receivers capable oflong usage times from small and lightweight hat
`In addition. the my: transmit power allows paging signals to ean'ly penetrate building
`Paging service also costs less than cellular service, both for the initial' device and 1
`monthly usage charge, although this price advantage has declined considerably in
`years a cellular prices dropped The low cost, small and lightweight handsets, long i
`life. and ability ofpaging devices to work almost anywhere indoors or outdoors are the
`reasons for their appeal.
`Barty radio paging systems were analog l-bit messages signaling a user that set
`wastryingtoreachhim-orher. These systemsrequiredcallhackoveralandlinetele
`to obtain the phone number of the paging party. The system evolved to allow a shor-
`tal message, including a phone number and brief text, lobe sentto thepagee as well.
`paging systems were initially extremely auccessfirl. with a peak of 50 million enlist
`in the United States alone. However. their popularity began to wane with the wide:
`penetration and competitive cost of cellular telephone systems. Eventually the comp
`from cellular phones forced paging systems to provide new capabilities. Some implen
`“answer-back” capability (i.e., taro-way communication). This required a major chat
`design of the pager because now it needed to transmit signals in addition to receiving
`andthe transmission distance to a satellite or base station can be very large. Paging
`panics also teamed up with palmtop computer makers to incorporate paging function
`these devices [18]., Despite these developments. the market for paging devices has a
`Considerably. although therein still a niche market among doctors and other profess
`who must be reachable anyWhere.
`
`1.4.1 Satellite Networks
`
`Commercial satellite systems are another major component of the wireless communic
`infrastructure [2: 3]. Geosynchronous systems include lmnarsat and Omni’I'RACS. Ti
`mer is geared minty for analog voice transmission from remote locations. For exampl
`commonly used byjorn'nalists to provide live reporting from war zones. The first-gene
`lnmarsat-A system was designed for large (l—m parabolic dish antenna) and rather it
`sive terminals. Newer generations of lomarsats use digital techniques to enable an
`less expensive terminals. about the size of a briefcase. Qualcomm’s Omni’l'RACS ptt
`two-way communications as well as location positioning. The system is used priman'
`alphanumeric messaging and location tracking of trucking-fleets. There are several
`difficulties in providing voice and data services over geosynchnonous satellites. It tr
`great deal o‘fpowerto reach theae satellites. so handsets are typically inc and bulky.
`dition. there is a large round-trip propagation delay; this delay is quite noticeable in twr
`voice communication. Geosynchronous satellites also have fairly low data rates of les
`10 ltbps. For these reasons. lower-orbit LEO satellites were thought to. be a better mat
`voice and data communications
`
`LEQ systems require approximately 30—80 satellites to provide global coveragt
`plans. for deploying such constellations were widespread in the late l9903. One of the
`ambitious oftheae systems, the iridium constellation, was launched atthat time. Hov
`the cost to build, launch. and maintain these satellites is much higher than coats for tern
`base stations. Although these LEO systems can certainly complement-terrestrial ayate
`low~popnlation areas and are also. appealing to unvelers desiring just one handset and 1
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`15.6 IMRGYCONSIMHED WORKS
`
`separating the cooperating nodes. When there is less of a difi‘erence between the sepa
`of the cooperating nodes and the transmission distance between these clusters. the e
`cost required for the local exchange of information exceeds the energy benefits of or
`sting. Cooperative MlMO is one form of coopermive diversity. Others were discus:
`Section l6.3.3. and these other mclmiques may provide energy savings comparable to
`needing those of cooperative MEMO, depending on the network topology.
`
`16.6.3 Access, Routing. and Sleeping
`Random access schemes can be-rnade more energy efficient by (i) minimizing collisiot
`the resulting retransmissions and (ii) optim‘zlng transmit power to the minimum tor
`for successful transmission. One way to reduce collisions is to increase error protect
`collisions become more tiequenr [Ill]. Altemativ'ely. adaptively minimizing power th
`probing as part ofthe random access protocol ha been shown to significantly increase e
`efficiency [111; 38]. Another method for energy-eficient access is to formulate the d
`umd access problem using a game-theoretic approach, where energy and delay are
`associated with the game [112]. Several difi'erent approaches to energy-efficient access
`evaluated in [113]. However. noclear winneremerged because the performance of eacl
`tocol is highly dependent on channel characteristics. Delay and fairness constraints on
`be incorporated into an energy-efficient access framework. as investigated in [114]. Mr
`these techniques avoid collisions through a version of TDMA. although setting up ch:
`ized aeces s‘undcr distributed control can lead to large delays.
`If users have long strings of packets or a continuous stream of data. then random 1
`works poorly since most transmissions result in collisions. Hence channels must be ass
`
`to users in a more systematic fashion by transmission scheduling. Energy constraints
`new wrinkle to scheduling optimization. In [100] it was shown that the energy requi:
`send a bit is minimized by transmitting it over all available bandwidth and time dimen
`However. when multiple um wish to ”access the channel, the system time and band
`resources mustbe shared among all users More recem work has investigated optimal s
`uling. algorithms to minimize transmit energy for multiple users sharing a channel [11
`this work, scheduling was optimized to minimize the transmission energy required by
`user subject to a deadline or delay constraint. The-energy minimization was based on
`ciously varying padeet transmission time (and corresponding energy consumption) to
`the delay constraints of the data. This scheme was shown to be significantly more e
`efficient than a deterministic schedule with the same deadline constraint.
`
`Energy-constrained networks also require routing protocols that optimize routes re
`to energy consumption. Ifthe rate of energy consumption is not evenly distributed acre
`nodes then some nodes may expire sooner titan others, leading to. a- partitioning of tin
`work. Routing can be optimized to minimize end-to-end energy Consumption by Q;
`the standard optimization procedure described in Section 16.3.3, with energy per hop (in
`of congestion or delay) 6 the hop cost [116]. Alternatively. the room canbe computed '
`on costs associated with the batteries in each node — for example, maximizing the mini
`battery lifetime across all nodes in the network [116; [17]. Different cost functions to
`mize energy-constrained routing were evaluated via simulation in [116] and were all to
`equivalent. The cost function can also be extended to include the traditional metric of
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`562
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`AD not: WIRELESS um
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`along with energy [118]. This method allows the route optimization to trade off betwer
`lay and energy consumption through different weighting of their respective contribut
`the overall cost function. Note that computation and disseminationotrouting tables cl
`tail significant cost: this can be avoided by routing traffic geographically (i.e., in the gr
`direction of its destination). which requires little advance computatibn [119].
`Energy-constrained nodes consume significant power even in standby mode, when
`arejust passive participants in the network with minimal exchange of datato maintait
`network status. The paging industry developed asolution to thistprohlem several cloud.
`by scheduling “sleep” periods for pagers. The basic idea is that each pager need only
`fortransmissions during certain short periods oftime. This is a simple solution toimph
`when a central controller is available. but iris less obvious how to implementsuch-stra
`within the framework of'disnibuwd network control. Sleep decisions must take into ac
`network connectivity, so it follows. that these decisions are local but not autonomous. i
`anisms that support such decisions can be based on neighbor discovery coupled with
`means for‘ordering decisions within the neigthrhood. in a given area, the opportun
`sleep should be circulated among the nodes, ensuring that connectivity is not. lost th
`the coincidence of several simultaneous decisions to sleep.
`
`16.6.4 Cross-Layer Design under Energy Constraints
`The unique attributes of energy-constrained networks make them prime candidates for-
`layer design. If node batteries cannot be recharged. then each node can transmit only a
`number of bits before it dies. after which time it is no longer available to perfonn its int:
`function (cg. sensing) or to participate in network activities such as routing. 'l'hus. e
`must be used judiciously across all layers of the protocol stack in orda- to prolong ne‘
`lifetime and meet application requirements.
`Energy efficiency at all layers of the protocol stack typically imposes trade-oil‘s be!
`energy consumption. delay, and throughput [120]. However, at any given layer, the 0;
`operating point on this trade-offcurve must be driven by considerations at higher layer
`example, if a node transmits slowly than it conserves transmit energy. but this compl
`access for other nodes and increases end-to-end delay. A routing protocol may use i
`trally located node for energy-efficient routing, but this will increase congestion and
`on that route and also burn up that node’sbattery energy quickly. thereby removing it
`the network. Ultimately the trade-05s between energy. delay. throughput, and node lne
`lifetime must be optimized relative to the application requirements. An emergency r
`operation needs on-the-scene information quickly. but typically the network supportin
`local information exchange‘need only last a few hours or days. In contrast, a sensor ne
`embemd into the concrete of a bridge to measure stress and strain must last decades. tl
`the information need only be collected every day or week.
`
`16.6.5 Capacity per Unit Energy
`When transmit energy is constrained, his not possible to transmit any finite number r
`with asymptotically small error probability; This is easy to see intuitively by consit
`the transmission of a single bit. The only way to ensure that two different values in :
`space (representing- the two posfible bit values) can be decoded with militarily small
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`Rembrandt Wireless
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`Apple Inc. v. Rembrandt Wireless Technologies, LP, IPR2020-00034
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