Performance parameters evaluation in broadband access network

In modern, competitive, and dynamic access networks the underlying bandwidth distribution mechanism has to be capable of understanding user requirements, meeting stringent quality of service (QoS) demands, and satisfying a broad spectrum of user traffic dynamics. Undoubtedly, optical fiber is the dominant transmission medium enabling practical and cost-effective optical infrastructures in the last mile. Passive optical networks (PONs) represent one of the most promising player towards the fiber to the home (FTTH) vision allowing users to experience high quality, demanding multimedia services and applications. The 10-gigabit-capable passive optical network (XG-PON), one of the latest PON standard, incorporates a set of profound conditions a contemporary PON should ensure. Fairness provisioning constitutes one of the most critical features a PON should provide. However, ensuring fairness in an access network with numerous different users, requesting multiple traffic flows in any time, is not a straightforward task. In this work, we focus on the fairness issue by devising an adaptive, efficient, and fair dynamic bandwidth allocation (DBA) scheme called Insistent FAIr STrategy prOcesS (IFAISTOS). IFAISTOS investigates and maintains user traffic profiles. Overloaded users are carefully treated by gaining greater granting windows than other users; however bandwidth monopolization is prevented. Fairness is ensured for all users in terms of traffic load and average delay. A steering, adaptive mechanism records user traffic profiles by changing and defining bandwidth weights proportional to individual traffic needs. Extensive simulation results reveal the efficacy of the proposed DBA in terms of fairness and average packet delay.

The development of protocol standards and the low cost of wireless equipment increased the number of wireless network installations in public (airports, universities campuses) and private (enterprises, homes) areas all over the world. This research effort examines the IEEE 802.11 protocol that dominates wireless local area networks (WLANs). Specifically, it investigates the performance of the Distributed Coordination Function (DCF) of ΙEEE 802.11 Medium Access Control (MAC) protocol. The objective of this thesis is to contribute in the research for the development of a simple and effective MAC sub-layer for WLANs that utilize the IEEE 802.11 protocol. Mathematical models are developed to calculate the following metrics in order to examine the performance of DCF that use Binary Exponential Backoff (BEB) algorithm: a) average packet delay per backoff stage and probability per backoff stage b) average packet delay, c) packet jitter, d) packet drop probability, e) average packet drop time, f) packet delay distribution, and g) cumulative packet delay distribution. An admission control algorithm is also presented. The proposed mathematical models are a) simple, as expressed with relatively simple mathematical relations, b) accurate, since they are validated by comparing analytical against simulation results and show that the proposed models are fairly accurate, and c) provide results in short period of time. Different scenarios of WLANs are examined to investigate the effect of DCF parameters in performance and to define the system parameters values that improve the performance of the IEEE 802.11 protocol. The analysis of metrics and the application of their outcomes to WLANs contribute in the design and development of more efficient access methods to wireless medium. The main contribution of this thesis is that packet delay is investigated thoroughly as a measure of WLAN performance.%%%%Η ανάπτυξη προτύπων για τα ασύρματα τοπικά δίκτυα σe συνδυασμό μe το χαμηλό κόστος της ασύρματης τeχνολογίας eπέτρeψe την ραγδαία eξαπλωση των ασυρμάτων δικτύων σe κοινόχρηστους και σe ιδιωτικούς χώρους όπως πανeπιστήμια, πλατeίeς, αeροδρόμια, γραφeία eπιχeιρήσeων, οικίeς, κλπ. Η παρούσα διατριβή μeλeτά το πρωτόκολλο ΙEEE 802.11 το οποίο κυριαρχeί στα ασύρματα τοπικά δίκτυα. Eιδικότeρα eρeυνά την απόδοση της κατανeμημένης διαδικασίας πρόσβασης DCF του υποeπιπέδου MAC του ΙEEE 802.11. Σκοπός της παρούσας eρeυνητικής προσπάθeιας eίναι η συμβολή στην έρeυνα για την ανάπτυξη eνός απλού και αποτeλeσματικού υποeπιπέδου πρόσβασης μέσου MAC στα ασύρματα δίκτυα που βασίζονται στο πρωτόκολλο ΙEEE 802.11. Αναπτύσσονται μαθηματικά μοντέλα για τον υπολογισμό των ακόλουθων μeτρικών για την απόδοση της διαδικασίας DCF που χρησιμοποιeί τον αλγόριθμο eκθeτικής οπισθοχώρησης ΒEΒ: α) την μέση καθυστέρηση των πακέτων ανά βαθμίδα οπισθοχώρησης και την πιθανότητα ανά βαθμίδα οπισθοχώρησης, β) την μέση καθυστέρηση των πακέτων, γ) την κατανομή των καθυστeρήσeων των πακέτων, δ) την αθροιστική κατανομή των καθυστeρήσeων, e) την διακύμανση των καθυστeρήσeων των…

Wireless Local Area Networks (WLAN)s are today common for access to Internet; well-known and used is IEEE 802.11 standardized technology. Some drawbacks of the standardized distributed medium access scheme, Distributed Coordination Function (DCF) has resulted in considerations made to extend the DCF from single-hop communications to multi-hop. Multihopping has the potential to reduce energy consumption and increase throughput and coverage. The drawback is lack of Quality-of-Service (QoS) support, which already with single-hop communication was bad, but extending a communication between two peers to multi-hop significantly reduces the possibility to offer reliable transmissions. The contention-based medium access performed at each hop with the DCF results in large uncertainties as to when a packet arrives to its end-destination. There are two general approaches for extending the DCF with QoS functionality: 1. Allocate resources for a flow and 2. Assign a flow higher priority than other flows. My hypothesis is that for strict QoS guarantees, a reservation-based approach is the better one. This has been my motivation to design a new medium access protocol; based on the DCF, periodic time slots for QoS-demanding real-time applications are reserved. The Distributed Allocation of time slots for Real-time traffic (DARE) is unique as it totally distributed sets up an end-to-end reservation before the transmission of data begins, repairs broken reservations, support many periods and time slot sizes and distribute piggy-backed information even to a two-hop radius from a receiver. This thesis describes the DARE protocol and also presents results from comparisons of DARE, DCF and the IEEE 802.11 E standardized priority-based QoS medium access protocol Enhanced Distributed Channel Access (EDCA). Using simulations, this thesis shows that DARE offers constant end-to-end packet delay for a flow, very low average packet delay in the whole system and constant throughput. EDCA and DCF depend strongly on the total network load; average packet delay for a real-time flow increases rapidly with the surrounding load. DARE outperforms both DCF and EDCA when many flows are present, even in networks with frequent topology changes where reservations must be repaired. Thus, the reservation-based DARE protocol is the most suitable approach for extending DCF with QoS.

There is a lack of high-speed and low-cost wireless network at sea to meet the increasing need of maritime users. With this observation, we have envisaged a WiMAX mesh network for high-speed ship- to-ship/shore communications. Analysis of interference range in such maritime WiMAX mesh networks is presented in this paper. And based on the findings, scheduling transmission of MAC control messages and data packets within three-hop neighborhood is investigated for the purpose of minimizing interference. A model is developed for analysis of the interference range in maritime environment. With parameter values that are derived from measurements at sea, we show that by scheduling among three-hop neighborhood the probability a transmission being interfered by a concurrent transmission drops about 30%. Simulation results show that, with the simulation settings in this paper, by scheduling among three-hop neighborhood, the initial packet delay and the average packet delay can be reduced by about 17% and 15.6% in sea state 3.0, respectively. In sea state 6.0, the performance improvement in initial packet delay and average packet delay are about 45% and 19.3%, respectively.

The first widely used communication infrastructure was the telephone network, often known as a connection-oriented or circuit-switched network. While making a phone call, these networks will first set up a connection, and then tear it down after the call has ended. The connection made during the call would not be used again. Thus, connectionless or packet-switched networks have been introduced, with an aim to send voice signals as data packets. When compared to conventional network architecture, SDN's separation of the data plane and control plane of networking devices makes the management of these devices directly programmable via a centralised controller. It uses a MAS-based distributed architecture to categorise network flows, and it's called the Traffic Classification Module. Each host or server's high-priority application traffic is isolated via Deep Packet Inspection (DPI). The time consumed for a packet to travel from one endpoint to another is referred to as the average packet delay, whereas the controller's reaction time is twice the average packet delay. Few works existed that utilised routing strategies to decrease the typical packet delay in SDN. To reduce the controller's response time, Software-Defined Networks (SDNs) need a routing algorithm that reduces the average packet delay. Each of the proposed modules and the whole combined SDN-MASTE framework were put through their paces in a series of experiments and emulation-based tests to see how well they performed.

Many diverse high bandwidth consumers of different quality of service (QoS) requirements can currently be well supported by the last mile candidate—gigabit Ethernet passive optical network (GE-PON) system. Through modeling the performance of TCP over GE-PON in terms of fairness among multiple optical network units (ONUs) and multiple transmission protocols, the results indicate that TCP flows will suffer from restraining windows when competing with other TCP or other protocol flows, such as UDP protocol flows. Therefore, this paper proposes an adaptable approach to promote the throughput of restraining TCP flows to achieve TCP fairness. This paper focuses on the potential benefits of such a recovery modification process for TCP flows. TCP flows are always considered as the low -priority services and suffer from best-effort delivery. The comparison in both experiments and simulations shows that restraining window elastic recovery (RWER) can improve inter-protocol fairness and achieve the TCP throughput enhancement.

One of the major challenges in long reach passive optical network (LR-PON) is the longer end-to-end traffic delay between the central office (CO) and the end user. This longer delay significantly hampers the quality of services (QoSs) of the optical access networks. The QoSs of the LR-PON are easily affected by delaying or dropping packets as a consequence of parameters such as latency, jitter, bandwidth utilization and packet loss. Most of the studies have only focused on capacity allocation amongst the multiple optical network units (ONUs) of the network by the optical line terminal. Some research also proposed to schedule the packets in multiple threads based on the priority. However, due to the lacking of intra thread scheduling scheme the high priority (HP) data packet still suffering from more delay. In this paper, we propose a decentralized intrathread scheduling scheme that provides lower queuing delay as well as end-to-end packet delay of the HP traffic. The performance measurements involve several scenarios which combine different traffic types, intra ONU scheduling and queuing policies. The goal of this research is to identify the most suitable scenario to provide qualitative services and efficient resource utilization among different traffic types. The performances of the proposed scheme have been analyzed and compared with the existing scheme by numerical simulations. The numerical results proves the advantages of the proposed scheme over the existing one in terms of lower average packet delay of high priority data packets and higher network throughput under varying offered loads.

The dynamic frame sizing algorithm is a throughput-optimal algorithm that can achieve maximum network throughput without the knowledge of arrival rates. Motivated by the need for energy-efficient communication in wireless networks, in this paper, we propose a new dynamic frame sizing algorithm, called the Greenput algorithm, that takes power allocation into account. In our Greenput algorithm, time is partitioned into frames, and the frame size of each frame is determined based on the backlogs presented at the beginning of a frame. To obtain a good delay-energy efficiency tradeoff, the key insight of our Greenput algorithm is to reduce transmit power to save energy when the backlogs are low so as not to incur too much packet delay. For this, we define a threshold parameter $T_{\max }$ (for the minimum time to empty the backlogs with maximum power allocation), and the Greenput algorithm enters the (mixed) power-saving mode when the backlogs are below the threshold. Using a large deviation bound, we prove that our Greenput algorithm is still throughput optimal. In addition to the stability result, we also perform a fluid approximation analysis for energy efficiency and average packet delay when $T_{\max }$ is very large. To show the delay-energy efficiency tradeoff, we conduct extensive computer simulations by using the Shannon formula as the channel model in a wireless network. Our simulation results show that both energy efficiency and average packet delay are quite close to their fluid approximations even when $T_{\max }$ is moderately large.

Internally buffered multistage interconnection network architectures have been widely used in parallel computer systems and large switching fabrics. Migration from electrical domain to optical domain has raised the necessity of developing node architectures with optical buffers. Cascaded fibre delay line architectures can be seen as possible realizations of output and shared buffering in a 2 × 2‐switching element. These approaches can be used as buffered node architecture in a Banyan like interconnect.In this paper, we investigate and compare these approaches by using simulation methods. Different performance metrics, such as normalized throughput, average packet delay, packet loss rate and buffer utilization have been used under uniform and non‐uniform traffic models. Results show that the TC‐chain node Banyan network offer an improved normalized throughput and average packet delay performances under both traffic models without disrupting first‐in‐first‐out order of arrivals. The switched delay‐line requires fewer switching elements than TC and TTC architectures but at the cost of high packet delay. Copyright © 2004 John Wiley & Sons, Ltd.

A Forward Resource Reservation (FRR) scheme for Optical Burst Switching (OBS) systems which can reduce the average packet delay during burst assembly is proposed. Mathematical analysis and the simulated performance are in line and validates that average packet delay can be significantly reduced by using the proposed algorithm. The main idea of FRR is to send Burst Header Packet (BHP) before the data burst is assembled. The FRR has been applied to time based, size based and mixed time and size threshold based approaches. The average packet delay and burst sizes have been studied in the three cases.

Due to the ever-expanding applications of the Internet-of-Things (IoT), designing energy- and spectrally-efficient transmission schemes to support massive connections and devices is inevitable and still challenging. Thus, energy-harvesting (EH) and cognitive-radio (CR) systems are becoming more inseparable for future IoT networks. This paper analyzes the performance of EH-CR-IoT networks, where closed-form expressions for network metrics, such as GoodPut, collision probability and average packet delay are derived. In addition to the interference caused by spectrum sensing errors, our analysis also incorporates the primary user (PU) return interference into the different network metrics. Furthermore, the effect of primary network traffic behavior and IoT network parameters are investigated. To account for delay-sensitive packets, the average end-to-end delay of packets as well as delay violation probability in the IoT network are mathematically formulated and analyzed as quality-of-service (QoS) measures for network stability. Moreover, the derived metrics can be utilized to optimize the Goodput, subject to various practical constraints. Simulations are also performed to verify the theoretical results. Above all, the effect of energy-harvesting rate on GoodPut and IoT network stability is explored, which provides insights into determining the physical structure of the energy-harvesting system.

In this paper, we evaluate the performance of multicasting in a single-hop local lightwave network based on a broadcast-and-select system. We use an approximate analytical solution and Markov model to show the effect of tuning time on the average packet delay and offered load. We also show the trade-off between the average packet delay and the number of wavelengths for the network.

Current and planned solutions used in the ICT infrastructure are largely based on Photonic and RF Communications Systems. Rapid advances in photonic and RF photonic technologies have significantly accelerated the introduction of these new technologies in access storage, backbone and grid networks, defining and building the rules to ensure transfer of multi Tera-bit volumes of data. The purpose of this volume is to provide a vehicle for directing research in this area from multiple lenses in the selected areas of investigation. Following an introduction by the editors, reviews of research will be clustered into two sections. The first part of this Special Issue focuses on the Photonic and RF Communications systems technologies and this Section comprises 7 articles. Recent solutions in wideband and multi-band RF circuits are presented in the articles 7 through 9 in the second part of the Special Issue. The first article, by Arash Bahrami , et al., present an experimental evaluation of a radio-over-fiber system. In the paper, the authors proposed an optical microwave radio-over-fiber system in which an integrated dual-parallel Mach-Zehnder modulator is biased at the maximum transmission biasing point. The authors consider the two following modulation schemes: binary phase shift keying (BSK) and quadrature phase shift keying (QPSK) over fiber spans of 10 and 25 km of standard single mode fiber. The obtained results show that the second order sideband of optical microwave has the potential to provide error-free transmission for BPSK and QPSK. John S. Vardakas , et al. in the next article, analyse the delay of converged Wavelength Division Multiplexing Ethernet Passive Optical Network and WiMax networks. In such access networks, the provision of Quality of Service (QoS) support is a challenging issue, mainly due to the different bandwidth allocation mechanisms of the two access technologies. In the paper, the authors analyse the delay performance by considering multiple service-classes with different priorities. The proposed analytical model allows the calculation of the average end-to-end packet delay of each service-class as the sum of the queuing delay in both domains. The accuracy of the analysis was verified by simulation. Ioannis Mamounakis , et al., propose a novel traffic prediction method to minimize packet delay in Ethernet Passive Optical Networks. The authors utilise traffic information to predict the accumulated burst size of each respective optical network unit in the following cycle. The paper demonstrates and proves that a significant delay enhancement can be accomplished by reporting the predicted burst size, rather than the current one, to the Optical Line Terminal (OLT). The simulation experiments carried out by the authors show that a significant decrease in the delay can be obtained without any changes to the dynamic bandwidth assignment scheme at the OLT. The paper by Mariusz Głąbowski , et al. proposes an analytical model of a multi-service switching network with overflow links with finite capacity in the first stage of the network. This model can be used to evaluate the QoS parameters which are closely interrelated with the method of operation of the large capacity optical nodes. The proposed method allows their traffic capacity to be increased through a significant decrease in the phenomenon of internal blocking in switching networks which is the basic element of the node. The proposed calculation method is validated by the authors via simulation. Aboagela Dogman , et al. present an integrated QoS management process for multimedia traffic in wire and wireless networks. In the proposed process, the statistics of traffic are determined and then used as an input to a fuzzy interface system (FIZ). FIZ allows the traffic to be accurately sampled and this traffic is in the next step pre-processed using a fuzzy c-means (FCM). FIZ identifies clusters representing poor, average and good QoS. This information is then used in a multilayer perceptron neural network to assess the overall QoS for multimedia traffic. The authors showed that the developed adaptive statistical sampling represents traffic more correctly than systematic, stratified and random non-adaptive sampling methods. The article by Adam Kaliszan , et al. provides a generalised convolution algorithm for modelling state-dependent systems. This model corresponds to the system that uses one or many physical resources, e.g. one or a set of lambda channels in DWDM optical networks. The proposed calculation method can be used for the analysis and dimensioning of optical networks and systems. This method is also useful for an optical system in which advanced traffic management mechanism have been applied, e.g. bandwidth reservation or threshold mechanism. The accuracy of the proposed model is validated by simulation experiments. From their onset RF Communications Systems have been critical to the development of ICT infrastructure. In mobile and satellite communication systems, wideband and multi-band RF circuits are important for achieving high-date wireless transmission and supporting a large number of standards (e.g. UMTS, WiFi, WiMAX, or LTE). A wideband or multi-band RF circuit can replace a number of single-band RF circuits, leading to a significant reduction of size, weight and cost of modern wireless systems. There have been a great number of recent developments in the above areas over the past years. The articles that outline these solutions are in the latter part of this Special Issue, i.e. comprise articles from Article 7 through Article 9. The article by Bingo Wing-Kuen Ling , et al. discusses the frequency spectrum of a pulse for ultra wideband impulse radio systems as the frequency response of a real valued causal rational infinite impulse response filter. The pulse design problem is formulated as a functional inequality constrained optimization problem that can be solved by the method proposed by the authors. This pulse can be generated via an excitation of a simple circuit. Numerical simulation results confirm that the energy compaction performance defined in the frequency domain of the proposed pulse outperforms that of existing pulses. It is worth emphasizing that the pulse can be generated via an excitation of a simple circuit. In their article, Xue Li and , et al. present the WiFi leakage problem that appears in the users' equipment that simultaneously use both LTE and WiFi technologies. The authors propose WiFi leakage detection algorithms for successful detection of the weak WiFi leakage in the presence of both LTE signal and Gaussian noise. The algorithms include energy ratio detection, entropy ratio detection and cyclostationary detection based on spectral correlation function. The effectiveness and efficiency of the proposed WiFi leakage detection techniques have been confirmed by simulations performed for different scenarios. The article by Piotr Remlein discusses the performance of Intelligent Transportation Systems (ITS) that consists of satellite mesh networks. In the paper the author analyses a new power-limited and energy-efficient systems employing coded continuous phase modulation signals and with multiuser Frequency Division Multiplexed transmission. The results obtained by the author show that good performance of the proposed solution can be achieved by reducing the inter-carrier frequency spacing and using simple iterative ICI cancellation algorithm at the receiver. Based on the results, it can be concluded that this system might constitute a desirable option in ITS satellite mesh, ad-hoc networks. The objective of this Special Issue is to bring together the state-of-the-art research contributions that address challenges in emerging devices and architecture for photonic systems and RF circuits for wideband and multi-band communications systems. Due to the complexity and scope of the subject area, the set of articles presented attempts to address only some selected relevant issues. The Guest Editors believe though that the contributions included in the Special Issue will inspire the research activities of leading authors and scholars worldwide. The Guest Editors also expect this Special Issue to provide insight into the questions that they address as the presented articles expose important contributions to each of the relevant subject areas. Piotr Zwierzykowski received MSc and PhD (Hons) degrees in telecommunications from Poznan University of Technology, Poland, in 1995 and 2002, respectively. Since 1995 he has been working at the Poznan University of Technology, where he is currently an Assistant Professor. Piotr Zwierzykowski is the author, or co-author, of over 200 journals and conference publications and three books in the area of computer and communication networks. His research covers modelling and dimensioning of optical networks, teletraffic engineering and routing. He is a Senior Member of IEEE and the Secretary in the IEICE Europe Section. Steven Gao received a PhD degree from Shanghai University, P.R. China. He is a Professor and Chair in RF and Microwave Engineering at University of Kent, UK. His research covers smart antennas, satellite antennas, phased arrays, RF and microwave circuits (power amplifiers), satellite communications, UWB radars, synthetic-aperture radars and mobile communications. From 2007 to 2012, he was a Senior Lecturer and Head of Space Antennas and Microwave System Group at Surrey Space Centre, University of Surrey, UK. He has two books including “Space Antenna Handbook” (Wiley, 2012) and “Circularly Polarized Antennas” (IEEE-Wiley, 2014), published over 200 papers and holds several patents in smart antennas and RF. He is an IEEE AP-S Distinguished Lecturer and a Chair of LAPC 2013. He is an Invited Speaker at IWAT'2014 (Sydney), SOMIRES'2013 (Japan), APCAP'2014 (China), etc. He is an Associate Editor of Radio Science and the Editor-in-Chief for Wiley Book Series on "Microwave and Wireless Technologies". He is a Fellow of the IET. Wai Pang Ng received his BEng (Hons) Communication and Electronic Engineering and IEE Prize from Northumbria University, UK and PhD in Electronic Engineering from University of Wales Swansea, UK in 1997 and 2001, respectively. He is a Reader of Optical Communications at Northumbria University. From 2001 to 2004, he was a Senior Networking Software Engineer at Intel Corporation, before starting his academic career at Northumbria University. He has published over 80 journals and conference publications in the area of optical switching, optical signal processing and radio-over-fiber. He is a Chartered Engineer of the Engineering Council UK and a Senior Member of the IEEE. Currently he serves as the Chair of the IEEE UK&RI Communication Chapter. He was also the Co-Chair of the Signal Processing for Communications Symposium in IEEE International Conference on Communications (ICC) 2009 (Dresden, Germany) and now serves as the Publicity Chair of ICC 2015 in London. Zuqing Zhu received a PhD degree from the Department of Electrical and Computer Engineering, University of California, Davis, in 2007. From July 2007 to January 2011, he worked in the Service Provider Technology Group of Cisco Systems, San Jose, as a senior R&D engineer. In January 2011, he joined the University of Science and Technology of China (USTC), where he is currently an Associate Professor. He has published more than 100 papers in peer-reviewed journals and conferences. He has been in the technical program committees (TPC) of INFOCOM, ICC, GLOBECOM, ICCCN and etc. He is also an editorial board member of Elsevier Journal of Optical Switching and Networking, Springer Telecommunication Systems Journal, Springer Photonic Network Communications Journal and Wiley European Transactions on Emerging Telecommunications Technologies amongst others. He has received the Best Paper Awards from the IEEE International Conference on Communications (ICC) 2013, the IEEE Global Communications Conference (GLOBECOM) 2013, and the IEEE International Conference on Networking and Communications (ICNC) 2014. He is a Senior Member of IEEE and OSA.

Gigabit Ethernet Passive Optical Network (GEPON) is considered as the best access means for Triple Play due to its simple structure and low costs. However, the point-to-multi-points tropology endangers its security and users' privacy. By investigating the safety threats in GEPON, a timestamp-based encryption is presented. The timestamp used in ranging is extracted and embedded into Advanced Encryption Standard (AES) algorithm, therefore the encryption keys vary with time due to the different ranging time. this paper presents a new encryption method based on timestamp function. This method combines AES algorithm with timestamp to form keys for encrypting downstream data. By adding an encryption/decryption module in both Optical Line Terminal (OLT) and Optical Network Unit (ONU), unsafe keys transmission through channel can be avoided. In addition, the extraction and synchronization of timestamp, along with the dynamic update and synchronization of keys, are released. Experimental results show that the method has the advantages of low delay, high throughput and high security compared with the traditional encryption algorithm.After the theoretical analysis, the simulation results of proposed scheme are given, proving its validity.

In this paper, the average packet delay on IEEE 802.11 DCF under finite load traffic in multi-hop ad hoc networks is analyzed. We employ a Markov chain model to analyze the probability of transmission at each node in an arbitrary slot and derive the channel access delay. We model each node using an M/G/1 queue and derive the queueing delay. The model is extended from analyzing the single-hop average packet delay to evaluating the end-to-end packet delay in multi-hop ad hoc networks without assuming the traffic to be in a saturation state. To validate our analytic results, we have done extensive simulation. The analytic and the simulation results match very well.