Showing papers on "Cognitive radio published in 1994"

Multi-Carrier CDMA in Indoor Wireless Radio Networks

Abstract: This paper examines a novel digital modulation/multiple access technique called Multi-Carrier Code Division Multiple Access (MC-CDMA) where each data symbol is transmitted at multiple narrowband subcarriers. Each subcarrier is encoded with a phase offset of 0 or π based on a spreading code. Analytical results are presented on the performance of this modulation scheme in an indoor wireless multipath radio channel. Introduction This paper examines the performance of a new spread spectrum transmission method called “MCCDMA” in an indoor wireless environment. MC-CDMA may be a suitable modulation technique in the indoor environment where the dispersive character of indoor propagation [1] allows for the exploitation of this technique. With MC-CDMA, each data symbol is transmitted over N narrowband subcarriers where each subcarrier is encoded with a 0 or π phase offset. If the number of and spacing between subcarriers is appropriately chosen, it is unlikely that all of the subcarriers will be located in a deep fade and consequently frequency diversity is achieved. As an MC-CDMA signal is composed of N narrowband subcarrier signals [2] each with a symbol duration, Tb, much larger than the delay spread, Td, an MC-CDMA signal will not experience significant intersymbol interference (ISI). Multiple access is achieved with different users transmitting at the same set of subcarriers but with spreading codes that are orthogonal to the codes of other users. Basic Principles of MC-CDMA The generation of an MC-CDMA signal can be described as follows. As shown in Fig. 1, a single data symbol is replicated intoN parallel copies. Each branch of the parallel stream is multiplied by one chip of a spreading code of length N and then binary phase-shift keying (BPSK) modulated to a subcarrier spaced apart from its neighboring subcarriers by F/Tb Hz whereF is an integer number. The transmitted signal consists of the sum of the outputs of these branches. For F = 1, this scheme is similar to performing Orthogonal Frequency Division Multiplexing (OFDM) [3] on a Direct-Sequence spread-spectrum signal [4]. Recently, there has been a growing interest on idea of combining OFDM and DS-CDMA [5] [6] [7] [8] [9]. Modern DSP methods make the implementation of MC-CDMA feasible and attractive. With F = 1, the transmit bandwidth is minimized. However, larger values of F may be desired to further increase the transmit bandwidth, i.e., to achieve a larger frequency diversity gain, without increasing the complexity in signal processing due to large spreading factors,N. The transmitted signal corresponding to the kth data bit of themth user ( am[k] ) is (1) sm t ( ) cm i [ ] am k [ ] 2πfct 2πi F Tb t + ( ) Tb t kTb − ( ) cos i 0 = N 1 − ∑ = cm i [ ] 1 1 , − { } ∈

UHF propagation prediction for wireless personal communications

Abstract: Propagation characteristics of radio signals in the UHF band place fundamental limits on the design and performance of wireless personal communications systems, such as cellular mobile radio (CMR), wireless LANs, and personal communication services (PCS). Because the radio link is direct to each subscriber, the prediction of signal characteristics is most important in urban areas where subscriber density is high, and the buildings have a profound influence on the propagation. The paper starts by reviewing the characteristic signal variations observed in CMR systems employing high base station antennas to cover macrocells having radius out to 20 km. Theoretical models incorporating diffraction are shown to explain the observed range dependence and shadow loss statistics. For the low base station antennas envisioned to cover microcells of radius out to 1 km for PCS applications, signal propagation is more strongly dependent on the building environment and on the location of the antennas in relation to the buildings. Various levels of theoretical modeling of this dependence are discussed in conjunction with measurements made in various building environments. Finally, the paper discusses advances in site specific prediction for outdoor and indoor propagation. >

Radio having memory means for storing radio user validation code

Abstract: A radio (e.g. a cellular radio telephone) is provided which is capable of operating with a set of incoming and outgoing call functions. Removable memory means 132 are provided (e.g. a smart card) for storing radio function selecting information 133 and a radio user validation code. The radio communicates with a radio communications system in response to the code for enabling the radio to receive incoming calls at least. Radio function control means activate a subset of the call functions within the set of call functions in response to the radio function selecting information stored in the removable memory means.

Arrangement for and method of providing radio frequency access to a switching system

Abstract: A cellular communication system provides dynamic allocation of hardware resources and frequency spectrum. The cellular system includes a server which dynamically controls the assignment of radio ports to a first and second group; each group shares hardware resources. Radio ports assigned to a first group may be reassigned by the server to a second radio port group in response to a predetermined condition, such as when the number of active users in the first group approaches the maximum user capacity of the first group. The transceiver hardware of each radio port is pooled on a group basis at the server location. This increases the user capacity of any radio port of a group to equal the total user capacity available at that group, as well as making more efficient use of transceiver resources.

An Architecture and Methodology for Mobile-Executed Cell Hand-off in Wireless ATM Networks

Abstract: An architecture is presented for a high speed cellular radio access network based on ATM transport technology. Central to this approach is a new concept known as the virtual connection tree which avoids the need to involve the network call processor for every cell hand-off attempt. Such an approach can readily support a very high rate of hand-offs, thereby enabling use of physically small radio cells to provide very high system capacity, but may occasionally cause the volume of traffic to be handled by one cell site to exceed that cell site's capacity. A simple analytical methodology is developed which can be used for admission control, the purpose of which is to limit the number of in-progress calls such that two new quality of service metrics (overload probability and average time in overload) can be kept suitably low.

Method for controlling data transmissions on a single channel radio frequency network

Abstract: A site system for remotely monitoring and controlling portable machines is provided which includes a single channel radio frequency network. At least one portable machine has a microcontroller for controlling operation of the portable machine, a plurality of sensors for supplying machine operational data to the microcontroller, and a radio frequency transceiver unit. The radio frequency transceiver unit communicates with the microcontroller, and with the single channel radio frequency network. At least one host computer has a radio frequency transceiver unit. The host computer communicates with a predetermined portable machine by data transmissions on the single channel radio frequency network. A radio frequency protocol controls radio frequency data transmissions on the single channel radio frequency network.

On channel definitions and rules for continuous dynamic channel selection in coexistence etiquettes for radio systems

Abstract: Dynamic spectrum sharing between uncoordinated systems of the same kind or even between systems using different technologies is attracting an increasing interest. Closely related is also "bandwidth on demand" for different services within a system. Traditional frequency planning is more difficult and less spectrum efficient the smaller the cells become. For indoor cells the practical planning limit is definitely passed. Continuous or instant dynamic sharing makes it possible to avoid to plan the channel assignments within a system and between systems. This paper presents analysis and simulations on dynamic spectrum sharing. >

Proposal of Radio High-way Networks for future multimedia-personal wireless communications

Abstract: Air interfaces of the mobile communication is widely spreading, because of the diversified service demands, technology trends and radio propagation conditions. This paper proposes the Radio High-way Networks that is universally applicable for any mobile services and any mobile radio air-interfaces. The system is constructed by using microcellular radio links and wide-band optical virtual free spaces, and the radio signal is guided by the virtual free space as radio signal format. As one pragmatic solution for the Radio High-way Networks, we select the PAM/IM/TDMA methods and give the routing algorithm, required sampling frequencies and the available capacity.

Hand-off method and mobile station for spread spectrum mobile communication

Abstract: Radio zones 2a through 2d are each assigned radio frequency channels of the number corresponding to the zone traffic, one frequency f1 of the radio frequency channel is assigned in common to all radio zones, and radio channels of the same frequency are assigned spectrum spreading codes different for each zone. A mobile station is provided with two correlators 14 and 15. If the received signal level lowers when the mobile station stays in the radio zone 2a and is in conversation over the channel of a frequency f2, the mobile station once switches the communication to a channel of the common frequency f1 and continues the communication using one of the correlators, while at the same time the mobile station scans spectrum spreading codes for control channels of the respective radio zones by the other correlator for measuring the received signal levels of the control channels and determines a destination radio zone which provides the maximum received signal level.

Cellular radio base station and control for extending range to mobile stations outside radio cell

Abstract: In cellular radio networks with TDMA transmission, the maximum signal propagation time inside a radio cell limits its propagation to a maximum radius, e.g. to 35 km in the known GSM. To extend the radio cell, the invention provides a fixed base station (BTS) with a TDMA radio receiver (RX) and an additional TDMA radio receiver (RXe), which receives lagging TDMA radio pulses from mobile stations (MS3) that are positioned outside of the radio cells (C). In this way, the fixed base station (BTS) supplies an extended radio cell (Ce), in which however only the maximum signal propagation time corresponding to the maximum expansion of the (small) radio cell (C) requires compensation.

Adaptive omni-modal radio apparatus and methods for networking the same

Abstract: A frequency and protocol agile wireless communication product, and chipset for forming the same, including a frequency agile transceiver (2, 4, 6, 8, 10, 12), a digital interface circuit for interconnecting the radio transceiver with external devices, protocol agile operating circuit for operating the radio transceiver in accordance with one of the transmission protocols as determined by a protocol signal (38, 40) and an adaptive control circuit for accessing a selected wireless communication network and for generating the frequency control signal (34) and the protocol control signal (38, 40) in response to a user defined criteria. Additionally, a network and method of operating a network of wireless service providers adapted to interact with a plurality of omni-modal wireless products within a given geographic area in a manner to permit the wireless service providers to 'borrow' radio frequencies from other wireless service providers within the same geographic region is disclosed.

Advanced wireless access system

Abstract: This paper describes an advanced wireless system which is composed of a wireless access node, a wireless access point, and a multimedia portable terminal. The wireless access node and access point are connected by optical fibers to realize broadband and high quality transmission. The radio frequency spectrum is directly carried on optical fibers using "fiber radio" technologies. This advanced wireless system, the multimedia wireless access system, provides video and data communications as well as voice services.

Channel capacity of spatial division multiple access schemes

Abstract: The radio frequency spectrum for wireless communications is a finite and scarce resource, there is a fundamental limit on the radio channels which can be made available to mobile communication We study the capacity limit of a wireless system with multiple receivers using an information theoretic model We showed that the capacity region expands and varies between two boundaries depending on the relative positions of the users >

A new architecture for mobile radio with macroscopic diversity and overlapping cells

Abstract: A new mobile radio cell architecture is presented that reduces interferences, increases system capacity, improves transmission quality and allows uncritical handoffs. Two main features characterize our proposal: macroscopic diversity supply of mobiles by means of three base stations which leads to high carrier-to-interference ratios and link quality improvement, and overlapping cells, thereby introducing large handoff zones. This system is ideally suited for existing GSM-style digital cellular networks and allows a traffic capacity increase due to a frequency re-use factor of 3.

Functional approach to a hybrid wireless network for mobile stations

Abstract: The limited range of wireless mediums is often compensated for by a cellular topology controlled by base stations interconnected by means of a wired infrastructure. The size of the area covered by such networks varies a lot according to the wireless medium used. They do, however, share certain functionalities which are presented here in the form of a functional model. To simulate this type of hybrid network, it is necessary to identify all parameters involved which may have an influence. This preoccupation led to an Entity model which is detailed in this paper for the case of an infrared wireless LAN for in-house communications. The principal parameters are classified and assigned to entities. The interactions between these entities and the characteristics of the network are identified for a future simulation.

Radio system with permanent adaptation to need in capacity through command of sender and receiver

Abstract: A radio system, in particular a mobile radio system (MRS), is proposed which has radio interfaces (COMa) with modifiable parameters (Ta, Fa) which are defined and modified by the fixed radio station BS. The parameters are calculated in the fixed radio station on the basis of the required transmission capacity (CAPr) of a distant radio station (MSa) and on the basis of a calculation of free transmission capacity (CAPI) within a pre-defined frequency range. The parameters (Ta, Fa) are defined in order to set the transceivers in the fixed radio station and in the distant radio station in such a way that the required transmission capacity takes up the minimum amount of free transmission capacity. Efficient use is made of the frequency spectrum, with radio transmission being matched continuously to the capacity requirements of the mobile stations.

Hand-off method and mobile station for spread spectrum communications system

Abstract: Radio zones (2a through 2d) are each assigned radio frequency channels of the number corresponding to the zone traffic, one frequency (f1) of the radio frequency channel is assigned in common to all radio zones, and radio channels of the same frequency are assigned spectrum spreading codes different for each zone. A mobile station is provided with two correlators (14 and 15). For example, if the received signal level lowers when the mobile station stays in the radio zone (2a) and is in conversation over the channel of a frequency (f2), the mobile station once switches the communication to a channel of the common frequency (f1) and continues the communication using one of the correlators, while at the same time the mobile station scans spectrum spreading codes for control channels of the respective radio zones by the other correlator for measuring the received signal levels of the control channels and determines a destination radio zone which provides the maximum received signal level.

Solving the frequency assignment problem with simulated annealing

Abstract: Spectrum management is one of the most difficult tasks in communication engineering today, because the spectrum must be considered as a limited and therefore very valuable commodity for wireless transmission of information. Nevertheless, it is not very popular to consider spectrum management and especially the frequency assignment problem as an EMC problem. In the paper the authors emphasize the EMC aspects of the frequency assignment problem.

Radio link access procedure for a wireless access communications system

Abstract: This paper describes a link layer protocol that provides for reliable delivery of user data over a wireless channel. This radio link access procedure (LAPR) is based on LAPB (used by X.25) and LAPM (used by V.42 error correcting modems), but has some deviations due to the nature of the radio link; these similarities and differences are discussed. Coordination between LAPR and call control signaling is discussed. The wireless access communications system employs TDMA/TDM on the radio interface. >

Tracking strategies in wireless networks

Abstract: Tracking strategies for mobile users in wireless networks are studied. In order to save the cost of using the wireless links mobile users should not update their location whenever they cross boundaries of adjacent cells. This paper focuses on three natural strategies in which the mobile users make the decisions when and where to update: the time-based strategy, the number of movements-based strategy, and the distance-based strategy. We consider both memoryless movement patterns and movements with Markovian memory along a topology of cells arranged as a ring. We analyze the performance of each one of the three strategies under such movements, and show the performance differences between the strategies. >

Method for muting a radio

Abstract: When a portable radio (110) receives a transmission from a mobile radio (105), the portable radio (110) mutes a speaker volume of the portable radio (110) for a duration of the transmission from the mobile radio (105). In an arrangement of the mobile radio (105) and the portable radio (110) where both radios transmit and receive on a same communication resource channel and both radios are in close proximity, acoustic feedback may be avoided.

A Survey of Relative Spectrum Efficiency of Mobile Voice Communication Systems

Abstract: This paper provides definitions of spectrum efficiency for general communication systems, then simplifies the definitions so that the spectrum efficiency of several contemporary mobile radio systems can be easily compared. A variety of systems currently in use and proposed for near-term deployment are compared to analog FM dispatch radio. The calculations show a ratio of 1 million between the most efficient and least efficient of the systems considered. Based on these calculations, a comparison can be made between various technologies and their ability to deliver communication systems with a very high spectrum efficiency.

Packet diversity techniques for a broadband ATM-oriented radio indoor environment

Abstract: We consider a future indoor wireless network operating in the mm-wavelength radio spectrum and capable of supporting broadband services like video teleconferencing and transmission of high-resolution images on top of the traditional ones that include cordless telephony and paging Antenna diversity techniques-operating on a packet basis at both the macroscopic and microscopic levels-combined with coding are suggested as a means to improve the reliability of wireless connections and make feasible the extension of ATM-related protocols to the wireless domain >

Dynamic frame control for TDD based wireless LAN

Abstract: In a wireless LAN, the radio frequency is an essential resource, but, because this radio frequency is a restricted resource that is shared worldwide, its efficient usage is required. A frame and control structure is proposed to efficiently manage the unbalanced traffic between the uplink and downlink, and the fluctuations of the stations traffic. A prototype for a wireless LAN with a transmission rate of 1.5 Mbits/sec is suggested. It allocates slots to the stations dynamically depending on the traffic, and thus, the idle slots of the idle stations are shared with the heavy traffic stations, so the throughput is increased. As a result of an analysis, it was found that a dynamic transmission speed of between 1 kbits/sec to 1.47 Mbits/sec for each station, with a transmission delay of 0.5 seconds is possible. >

Design of common access channels for TDMA-TDD microcell communications systems

Abstract: This paper describes a detailed design of common access channels in the down link which are constructed with two transmission frames, multi-frame and super-frame, on a dedicated control carrier frequency in TDMA-TDD systems. The co-channel interference between TDMA-TDD bursts is discussed as the first consideration in the design of multi-frame. For the super-frame design, the average connection delay in a call control sequence is evaluated for the various period of super-frame as a function of offered traffic. A method of designing the optimum common access channels transmission frames is proposed. >

Mobile radio system with full-duplex and half-duplex traffic

Abstract: Both cellular mobile radio systems for full duplex communication between subscribers of the mobile radio system and network subscribers connected to the mobile radio system, and trunked radio systems are known in which subscriber groups can in each case exchange information with one another in half-duplex traffic. It is the object of the invention to specify a mobile radio system which exhibits greater flexibility and better frequency economy. By using switching means which switch an uplink radio channel to a downlink radio channel, subscriber groups with half duplex traffic can be formed in each full duplex mobile radio system, only one radio channel being needed for each subscriber group.

Microcell propagation prediction techniques

Abstract: The ability to accurately predict radio propagation characteristics for microcells is becoming crucial to the design of wireless communication networks. Several techniques have been successfully developed for the line of sight situation and the purpose of this paper is to comprehensively collate and review these results. The paper covers empirical and ray tracing propagation techniques, addressing the applicability of the methods and the directions for future work in the area of microcellular radio propagation prediction including considerations for the non-line of sight situation. >

Radio terminal equipment of mobile communication

Abstract: PURPOSE:To improve speech quality and the handleability accompanied by this when the radio terminal equipment of mobile communication is enabled to be used in two radio frequency bands. CONSTITUTION:This equipment is composed of reception means 111 to 115 of a 1.5GHz radio frequency band, transmission/reception means 121 to 125 and 131 to 135 of a 900MHz radio frequency band, reception means 211 to 215 of a 900MHz radio frequency band, transmission/reception means 221 to 225 and 231 to 235 of a 1.5GHz radio frequency band, two transmission/reception antennas 1 and 2, an antenna changeover switch 3 connecting the transmission/ reception antenna 1 with either one of the means 111 and 121 and an antenna changeover switch 4 connecting the transmission/reception antenna 2 with either one of the means 111 and 221.