Full Area Coverage Research Articles

Vision for 2020?

Mobile and wireless communications provide today high global penetration especially for voice and lower rate data services. In future such systems will be applied in many different usage scenarios from mobile and stationary applications in different radio environments for different communication relations between humans and machines. Today different types of systems are being applied for different application areas. In future, systems and applications will be mainly designed from a user-centric perspective. The vision of future systems is based on an integration and cooperation of different cooperating access systems in a heterogeneous environment at a packet-based core network. ITU-R provided this vision and basic requirements already in 2003, which are the basis for the preparation of World Radiocommunication Conference (WRC 2007) for the potential identification of additional frequency spectrum. In addition, international bodies and communities developed general vision statements on the future development and identified the necessary research areas. Availability of sufficient frequency spectrum is an issue for systems especially with high user throughput versus Quality of Service requirements for full area coverage. Limitations in the availability of sufficient frequency spectrum for wideband communication may change the role models for operators and may potentially result in infrastructure sharing. In the last years huge research activities have been launched in Asia, Europe and North America, which were originally triggered by the ITU-R vision and are following a similar technical approach. There are also parallel activities ongoing in the global wireless IT sector for different application scenarios. These developments have also to consider economic trends and a parallel deployment of wideband fixed line systems. This will result in different scenarios such as Fixed-Mobile-Convergence (FMC) versus competition between operators for mobile and/or fixed line services. In addition, an increasing use of IP for voice and data communication has to be considered in future system design. With respect to the huge deployed infrastructure future developments are expected to evolve from existing and emerging systems. However, all players have also to be prepared for disruptive developments driven by new players. This paper will provide an overview on these different trends and developments towards future systems.

Affordable Mobile TV Services in Hybrid Cellular and DVB-H Systems

Mobile TV services are expected to become a key application in future wireless networks. The recently proposed terrestrial digital broadcast technology, DVB-H, especially designed for mobile services, is regarded as a powerful alternative to the 3G cellular networks that already offer these services out on a point-to-point basis. Unfortunately, the cost of supporting real-time streaming and full area coverage seems to be very high compared to fixed TV services. In this article we discuss hybrid IP datacast DVB-H and 3G systems as a possible solution for providing affordable network infrastructure and services. Our approach is DVB-H centric. The 3G cellular system plays the role of providing interactivity, error reporting, and repair for the DVB-H broadcast channel. To enable an easy and efficient interworking of DVB-H and 3G, we employ forward error correction at the application layer with digital fountain coding. The main way to provide lower cost services is to avoid full DVB-H area coverage from the beginning and to perform an incremental DVB-H network deployment that follows the user demand. In this direction, to hide the discontinuity in coverage from the perception of users, we propose to take advantage of the bursty character of DVB-H transmissions and the mobility of users. This is possible by sending additional parity data, either with the DVB-H or the cellular network, in the time intervals between original service bursts. We evaluate the potential DVB-H infrastructure cost savings determined by transmitting additional parity data in DVB-H when targeting vehicular users. The implications of delivering parity data through the cellular network also are discussed. The numerical investigations show a potential for significant cost savings compared with the traditional approaches.

Innovative lens improves imaging for surveillance systems

Historically, the army, border-security agencies, and transportation-security planners have recognized the advantages of panoramic imaging systems that contain fields of view of up to 180◦ in their coverage areas. Such advantages include increased coverage with fewer cameras, simultaneous tracking of multiple targets, full horizon detection, and immersion capability. However, existing panoramic imagers like fisheye, mirror, and PAL (short for panoramic annular imager) have disadvantages related to the number of effective pixels (the basic unit for video screen images) used on their sensors. These disadvantages are due to blind zones and circular or annular (ring-like) image areas that are commonly called footprints. These drawbacks seriously reduce the use of panoramic imagers for surveillance. To solve these problems, we designed a new imager—the Panomorph lens—that incorporates the advantage of full-area coverage (with a 180◦ field of view) and the ability to increase resolution where needed. Thus, the Panomorph lens allows for a larger coverage zone and distributes its image more efficiently on the sensor.1, 2 Two important parameters for the Panomorph lens are the amount and location of the resolution. These parameters, introduced at the optical design stage, allow the Panomorph lens to provide a higher resolution in a defined zone than any other standard panoramic imager. By comparison, a fisheye lens on a standard NTSC camera (i.e. using the accepted television format in North America and Japan) requires up to six times more pixels on its sensor to produce the same resolution.2 For the security and surveillance of buildings such as indoor parking garages, corporate offices, retail stores, shipping ports, storage facilities, airport terminals, and residential homes, a camera is mounted to the ceiling with its lens facing down (see Figure 1, left). The most significant objects are located in the zone at the periphery of the lens, also called the green zone or zone of interest. The green zone is the most important part of the Figure 1. (left) A camera is mounted on the ceiling in an indoor surveillance application. (right) The graph shows the pixel-to-angle coverage, with the dashed line representing a linear pixel coverage.

Effects of Azolla species on weed emergence in a rice paddy ecosystem

The effects of Azolla pinnata R. Br. on weed emergence were evaluated in terms of plot area coverage by an A. pinnata mat, its biomass production and the amount of weed emergence, using fresh and dry weights, in a rice paddy field experiment. The experiment was conducted following a randomized block design with five combinations of fertilizer and A. pinnata treatments (control, A. pinnata + superphosphate, A. pinnata + urea, A. pinnata + compound fertilizer, A. pinnata + cow manure). The results revealed that after 18 days of inoculation, all superphosphate (T1) and cow manure (T4)‐treated plots were fully covered by the A. pinnata mat. However, coverage of the urea (T2) and compound fertilizer (T3)‐treated plots were only 80% and 70%, respectively. The full plot area coverage by the A. pinnata mat and the highest biomass production with superphosphate and cow manure‐treated plots were able to completely inhibit two weed species (Scirpus juncoides Roxb. var. hotarui Ohwi and Monochoria vaginalis Burm. f. Presl var. plantaginea (Roxb.) Solms‐Laub) and significantly suppressed four other weeds (Cyperus serotinus Rottb, Echinochla oryzicola Vasing, and Eclipta prostrata L.). In all the treatments, the fresh weight of weeds significantly reduced to 13, 29, 34, and 9%, respectively, for treatments T1, T2, T3, and T4. The dry weights also were significantly reduced to 10.00, 16.00, 22.00, and 7.26%, respectively, for treatments T1, T2, T3, and T4 over the control. The results revealed that there was a significant correlation among plot area coverage by the A. pinnata mat, its biomass production and weed emergence in a rice paddy field over the control. Azolla pinnata did not have any detrimental effect on the growth of rice plants.

Study of the 1997 Borneo fires: Quantitative analysis using global area coverage (GAC) satellite data

In 1997 a drought commenced in Southeast Asia, this being directly related to the then ongoing El Niño‐Southern Oscillation (ENSO) event. Interaction between land clearance activities and this drought led to massive, uncontrolled vegetation fires that burned large areas of forest and agricultural land, most severely on the Indonesian island of Borneo. A similar situation in 1982–1983 led to the largest uncontrolled forest fire ever documented, damaging around 50,000 km2 of Borneo's forest. This paper investigates the extent to which nighttime advanced very high resolution radiometer (AVHRR) global area coverage (GAC) data can be used to detail the spatial and temporal evolution of these large‐scale Indonesian fire events, and particularly the 1997 activity. GAC data are a spatial subsample of the full resolution local area coverage (LAC) AVHRR data, but unlike LAC, they have been archived globally on a daily basis for almost 20 years. Despite the extreme subsampling involved in GAC data production, simulation modeling and analysis of real data indicates that surprisingly reliable fire statistics can be obtained for the 1997 Borneo fire event from GAC imagery. For three dates in October 1997 where coincident LAC and GAC data are available, once numerical adjustment for the GAC subsampling procedure is included, fire counts extracted from LAC and GAC data consistently agree to within 0.15–13%. Time series analysis of the 1997 GAC data indicates that fires began in July in south Kalimantan, principally at the interface between cleared, cultivated land and lowland rain forest. Fire activity moved generally southward and peaked in September 1997. GAC data show the equivalent of 9733 LAC pixels as containing one or more active fires on 2 September. Fire activity declined significantly in November owing to the onset of the monsoon rains, with all fires ceasing by December 1997. Analysis of the cumulative fire map distinguishes peat swamp forest as the most severely affected ecosystem on Borneo, with >20% of this land cover category being identified as directly impacted by active fires. If the performance of GAC data can be shown to extend to other El Niño years and also to less intense periods of burning, then the GAC archive offers a tool for analyzing long‐term changes in the spatiotemporal pattern of fire activity in the region. Any trend can then be investigated for its relation to variations in agriculture, El Niño‐related climate, and other phenomena relevant to regional change in Southeast Asia.

Optimal merging of LAC and GAC data from SeaWiFS

We present a methodology to generate, from SeaWiFS data, 2-km resolution maps of the globe that optimally combine the full spatial resolution Local Area Coverage imagery received at ground stations, and the sub-sampled Global Area Coverage data recorded on board the satellite. Monthly maps display estimates of the Fraction of Absorbed Photosynthetically Active Radiation over terrestrial surfaces and the surface chlorophyll concentration over oceanic areas.

Design of a Catamaran Sounding Vessel for Operation in the St. Lawrence

CCG Laurentian Region currently operates three vessels whose primary function is the sounding of dredged navigation channels in the St. Lawrence from Montreal to Gap Gribane, 15 km downstream from lle d'Orleans. The vessels also provide services as far out as Rimouski and into the Saguenay. These vessels sound, on an annual basis, some 120 km2 of surface area. Due to its association with Seaway dredging in which some 0.3 million m3 of material is removed annually, this sounding activity has to be carried out with an accuracy greater than that normally associated with hydrographic charting. CCG Laurentian Region specialists have brought together current off-the-shelf sounding and position-keeping equipment which comprise a sounding mission system capable of onboard real-time data processing compatible with significantly higher sounding speeds than the 10 knots of the existing fleet. The existing fleet, which comprises two 18 m catamaran vessels and the shipping channel maintenance vessel Nicolet, is now approaching the end of its economic life and is scheduled for replacement. The replacement program comprises two catamaran vessels designed to sound at 18 knots, thus providing full area coverage in the 8-month operating season from mid-April to mid-November. This paper presents some of the challenges represented by the mission requirement and the engineering solutions incorporated into the vessel design.

Multifixed-beam satellite antenna with full area coverage and a rain-tolerant polarization distribution

Two problems of multifixed-beam satellite antennas have been 1) gaps in coverage in a given field of view, and 2) use of polarizations which are sensitive to cross coupling caused by precipitation in the earth's atmosphere. These problems can be solved, and in addition, large frequency reuse can be achieved, by application of cluster feeds to an offset Cassegrainian antenna. New features described here include a) interleaving of cluster feeds, b) use of linear orthogonal polarizations distributed to lie in local vertical and local horizontal planes on the earth's surface, c) clusters of keystone-shaped feed elements, d) a system for interconnecting uplink and downlink beams, and e) a method for evaluating aberration-sensitive antenna parameters. It is found that aberrations are negligible for beams aimed within the contiguous United States.

A Scanning Spot-Beam Satellite System

We propose a satellite with a high gain, movable spot beam to communicate with individual earth stations time-sharing a single channel in the tdma (Time-Division Multiple Access) mode. It is estimated that this approach could readily save some 20 dB in the link budget while still providing full U.S. coverage. When this 20 dB is apportioned with the objectives of reducing the earth-station antenna size, increasing the satellite capacity, and reducing transmitter power, the effects are dramatic. This technique can be combined with a fixed-spot beam system serving major traffic areas. This combination can provide both full area coverage as well as multiple reuse of the frequency band. A tdma burst organization is proposed, and estimates of burst lengths, beam switching intervals, and buffer storage size are made for a 100-earth-station network operating on a 600 Mb/s channel. A phased array antenna with each element irradiating the entire U.S. is employed to form the movable spot-beam. This provides an attractive solution even though a closed-loop beam-forming algorithm may be required. It appears feasible to construct such an antenna with nearly 50-dB gain capable of forming a spot beam toward any position within the continental United States with a switching time of a few nanoseconds.