Papers by Pentti Leppanen
5th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Wireless Networks - Catching the Mobile Future.
The linear equivalence of the binary Golay complementary sequence pairs is studied from the viewp... more The linear equivalence of the binary Golay complementary sequence pairs is studied from the viewpoint of feedback shift-register generators. Sequences that are synthesized by the concatenation and interleaving methods from the members of a basic code pair (the kernel) of lengths 2, 10 and 26 are considered. It is demonstrated that by the use of the Berlekamp-Massey shift-register synthesis algorithm the linear complexity value of complementary sequences is at least 3/4 of the sequence length. For some sequence pairs the linear complexity value can be even 0.98 times the sequence length. In the light of these results complementary sequences are considered suitable for information security applications employing the spread-spectrum (SS) technique in which strong non-linearity and good statistical properties are required for pseudonoise (PN) sequences.
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Ieice Transactions on Fundamentals of Electronics Communications and Computer Sciences, Apr 25, 1996
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1999 IEEE International Conference on Personal Wireless Communications (Cat. No.99TH8366)
Software radio development aims at wideband RF access and software partitioning for plug-and-play... more Software radio development aims at wideband RF access and software partitioning for plug-and-play type of use. The development is facilitated by progress in silicon capabilities, signal processing power of new and future processors and reconfiguration methods (software download, smart cards, etc.). However, there are still a lot of problems in implementing software radio. These problems include high quality wideband RF
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Broadband Satellite Communications for Internet Access, 2004
Some of the proposed Ka-band satellite systems will use ATM technology to seamlessly support Inte... more Some of the proposed Ka-band satellite systems will use ATM technology to seamlessly support Internet traffic. ATM was originally designed for fiber-based terrestrial networks that exhibit low latencies and error rates. With the increasing demand for electronic connectivity across the world, satellite networks play an indispensable role in the deployment of global networks. Ka-band satellites using the GHz frequency spectrum can reach user terminals across most of the populated world. ATM-based satellite networks can effectively provide real-time as well as non-real-time communications services to remote areas. [273, 274, 275]
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Broadband Satellite Communications for Internet Access, 2004
ABSTRACT Quality of Service (QoS) describes the guaranteed delivery of applications based on the ... more ABSTRACT Quality of Service (QoS) describes the guaranteed delivery of applications based on the low delay and packet loss requirements. A set of Service Level Agreements (SLAs) normally specify the QoS requirements as described in Chapter 5. QoS is delivered by restricting the total amount of traffic competing for the same amount of resources if the ingress traffic exceeds the minimum capacity of the network. The network capacity is effectively proportioned by the packet prioritization, so that higher priority traffic is unaffected by the lower-priority traffic. QoS guarantees can be made either over an aggregate of communication associations or individual flows. QoS is assured by reserving resources such as bandwidth and buffer space [238].
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Broadband Satellite Communications for Internet Access, 2004
ABSTRACT The rapid growth and ubiquity of the Internet is a major force driving the convergence o... more ABSTRACT The rapid growth and ubiquity of the Internet is a major force driving the convergence of data, voice, and video applications. However, applications like audio/video streaming, distance learning etc., demand significant bandwidth and have strict timing requirements. This necessitates the development of a new network infrastructure supporting beyond the simple best effort service that IP currently delivers. Satellite communications plays a significant role in providing access to the Internet through a hybrid — satellite/terrestrial or two-way IP network infrastructure. To provide a high data rate Internet access and global connectivity, provisioning of Quality of Service (QoS) within the next generation satellite systems is crucial. In this chapter, we discuss an end-to-end QoS layer model, QoS parameters, functional allocation, and QoS architectural standards. An overview of the core and access network QoS functions, mobile QoS followed by system availability considerations are described. This chapter provides the necessary background for conducting performance simulation to identify the critical parameters for implementation of satellite IP and/or satellite ATM networks. Some of these simulation models and performance results are discussed in parts Three and Four.
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Broadband Satellite Communications for Internet Access, 2004
ABSTRACT In the previous chapter, we discussed the design challenges at the networks are directed... more ABSTRACT In the previous chapter, we discussed the design challenges at the networks are directed towards multimedia services with new infrastructures including satellite, wireless, and optical technologies. Due to the simplicity and universality of IP, the network architectures will be based on IP or IP over DWDM. However, the provisioning of user level QoS and performance guarantees is a critical issue to be solved. The IETF proposed QoS mechanisms for terrestrial networks must be extended for satellite networks. In this chapter, we provide traffic management to deliver negotiated QoS to applications, congestion control followed by a discussion on QoS mechanisms subsequently identifying issues with Voice over IP over satellite. Other significant issues of IP Security, multicast over satellite, and forward and return protocol architectures for interactive IP satellite networks are discussed.
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Broadband Satellite Communications for Internet Access, 2004
We described the satellite link impairments and the necessary TCP enhancements for satellite netw... more We described the satellite link impairments and the necessary TCP enhancements for satellite networks in Chapter 7. Several design options exist for transporting TCP over satellite with onboard ATM switch. These design options include: (a) end system policies — Vanilla TCP, Selective ACK, Fast Retransmit, and Recovery (b) buffer management — Early Packet Discard (EPD), Tail Drop, per-VC accounting (c) feedback control—explicit rate, end-to-end, hop-by-hop and (d) queue management — per-class queuing, per-VC queuing. In the previous chapter, we described simulation results for buffer requirements using satellite ATM UBR service.
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Broadband Satellite Communications for Internet Access, 2004
The convergence of computer networks and telecommunication technologies resulted in the explosive... more The convergence of computer networks and telecommunication technologies resulted in the explosive growth of the global information infrastructure. The independent research on distributed communications at RAND (1964), Advanced Research Projects Agency Network (ARPANET) sponsored by Defense Advanced Research Projects Agency (DARPA) group (1967), and network research at The British National Physical Laboratory (1965) have resulted in the development of packet switched networks. In 1972, the materialization of an open networking architecture [1] and the Transmission Control Protocol/Internet Protocol (TCP/IP) formed the fundamental milestone for the successful development of the Internet. During early 1980s, TCP/IP included in the Berkeley UNIX operating system became popular for several network services. Subsequently, in 1986, National Science Foundation (NSF) funded a new high-speed backbone network called NSFNET. Another significant evolution of hypermedia software interface to the Internet, called World Wide Web (WWW) (1991) made the Internet extremely popular. In 1997, various Internet service providers (ISPs) reported traffic growth on Internet at the rate of 10–20% per month. Ever since, the Internet has evolved so fast, that it became a vital part of communication infrastructure across the globe.
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Proceedings of MILCOM '93 - IEEE Military Communications Conference
ABSTRACT This paper introduces the analysis and simulation results of a DS spread spectrum system... more ABSTRACT This paper introduces the analysis and simulation results of a DS spread spectrum system in which the principle of matched filter synchronization for acquisition of code synchronization is used. Mean acquisition time approximations of coherent matched filter synchronization in AWGN-channel, continuous and pulsed tone jamming, when complementary codes are used as the spreading codes, are indicated. The idea of using median type filtering as an aiding device for the matched filter is tested in those situations. It is shown that the performance degradation in AWGN-channel is not catastrophic due to use of the median filter. Continuous and pulsed tone jamming can have a very dramatic influence on mean acquisition time if the imbalances of the codes have large values. The influence of continuous tone jamming can be totally eliminated by using a median filter. Pulsed tone jamming can be eliminated almost totally, if jamming is pulsed so that it is on during some whole code periods. Simulations show that the jamming can be eliminated even if the jamming is pulsed in a way that it is on during some chips within every code period
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The authors point out the need for fixed PN code sets for test purposes from the standpoint of nu... more The authors point out the need for fixed PN code sets for test purposes from the standpoint of numerical analysis and simulation of an asynchronous DS-CDMA system and its sub-system units. An agreement on test sequence sets and their initial phases for fixing the probability distribution function of the multiple-access interference (MAI) random variable is necessary in order to make the numerical performance results of different research groups and authors commensurable in large system design projects and in the CDMA literature. The conclusions are drawn from numerical examples of initial-phase optimization with the auto-optimal least side-lobe energy (AO/LSE), least side-lobe energy auto-optimal (LSE/AO), maximum side-lobe energy auto-optimal (MSE/AO), cross-optimal minimum mean-square cross-correlation (CO/MSQCC) and minimum mean-square cross-correlation cross-optimal (MSQCC/CO) criteria and by reviewing the literature. Optimization criteria are compared from the standpoint of min...
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MILCOM 91 - Conference record
The performance of an asynchronous biphase coded direct sequence spread-spectrum multiple-access ... more The performance of an asynchronous biphase coded direct sequence spread-spectrum multiple-access (DS/SSMA) system is studied, when maximum length, Gold, and a small set of Kasami sequences are used as spreading codes. The signal-to-noise ratio (SNR) at the output of an asynchronous DS/SSMA receiver and the average interference parameter were used as performance measures. It was found that use of the
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MILCOM 91 - Conference record
ABSTRACT
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MILCOM 91 - Conference record
ABSTRACT The performance of a chip combiner and a signal-level-based erasure direct-sequence (DS)... more ABSTRACT The performance of a chip combiner and a signal-level-based erasure direct-sequence (DS)/BPSK receiver was analyzed with Monte-Carlo simulations in an additive white Gaussian noise (AWGN) channel and in pulsed WGN interference using BPSK modulation and an optimum convolutional code of constraint length 7 and code rate 1/2. The receivers employ a soft decision Viterbi decoder. The receiver structures eliminate the need for a fast-acting circuit. The chip combiner DS receiver proved to be the most robust in the pulsed WGN channel and may combat the effects of pulsed noise interference. A continuous noise jammer was the worst-case jammer. The coding gain of both receivers compared with the uncoded system was 13.5 dB in the worst-case interference at a bit error rate of 10-3
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Wireless Personal Communications, 2000
The authors point out the need forfixed PN code sets for test purposes from thestandpoint of nume... more The authors point out the need forfixed PN code sets for test purposes from thestandpoint of numerical analysis and simulation of anasynchronous DS–CDMA system and its sub-system units.An agreement on test sequence sets and their initialphases for fixing the probability distributionfunction of the multiple-access interference (MAI)random variable is necessary in order to make thenumerical performance results of different researchgroups and
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Broadband Satellite Communications for Internet Access, 2004
As we described in Chapter 1, Multiprotocol Protocol Label Switching has certain significant char... more As we described in Chapter 1, Multiprotocol Protocol Label Switching has certain significant characteristics due to integration of the ATM Quality of Service and signaling, and IP forwarding functionality. MPLS forwards the packets through fixed length labels and provides traffic engineering to guarantee the Quality of Service requirements. These concepts can also be extended to satellite networks and the advantages should be realized. To demonstrate such feasibility, we provide a simulation model for MPLS over satellite network. Examples of TCP and UDP flows are considered and QoS performance in terms of packet loss, delay, and jitter is discussed.
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Broadband Satellite Communications for Internet Access, 2004
The purpose of this chapter is to explore physical and link layer technical challenges and issues... more The purpose of this chapter is to explore physical and link layer technical challenges and issues for broadband satellite networks. Data traffic is growing at a much faster rate than voice traffic and there is a great interest among satellite network designers to apply advanced technologies to meet the emerging bandwidth-rich application requirements through existing and planned satellite transponders. To achieve this, at physical layer, higher order modulation, and efficient encoding techniques are extremely important. This chapter briefly discusses the physical layer issues including adaptive coding, and power control techniques. Subsequently, at the link layer, it presents an overview of the multiple access techniques covering fixed, random, and demand assignment with reservation control. These access schemes are compared in terms of throughput, collisions, and traffic handling capabilities. Bandwidth allocation is a challenge for Digital Video Broadcasting — Return Channel via Satellite (DVB-RCS) networks. A Combined Free Demand Assignment Multiple Access (CF-DAMA) scheme and its performance for DVB-RCS system are described.
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Papers by Pentti Leppanen