Search

The rapid advancement of communication technologies underscores the urgent need for robust and adaptable emergency communication systems (ECSs), particularly crucial during crises and natural disasters. Although network-based ECSs have been extensively studied, integrating open-source technologies, such as software-defined wide area networks (SD-WAN) with private long-term evolution (LTE) base stations, is a relatively unexplored domain. This study endeavors to fill this gap by introducing an experimental ECS platform that utilizes a hybrid network, incorporating a VoIP network to enhance open-source and on-premises communications in targeted areas. Our hypothesis posits that a hybrid network architecture, combining SD-WAN and private LTE, can substantially improve the reliability and efficiency of ECSs. Our findings, supported by the open-source OMNeT++ simulator, illuminate the enhanced communication reliability of the network. Moreover, the proposed platform, characterized by autonomous wireless 4G/LTE base stations and an Asterisk VoIP server, demonstrates improved quality of service (QoS) and quality of experience (QoE), with minimal data loss. This research not only has immediate practical applications but also bears significant implications for the development of cost-effective, open-source communication networks, optimized for emergencies, critical infrastructure, and remote areas.

The rapid advancement of communication technologies underscores the urgent need for robust and adaptable emergency communication systems (ECSs), particularly crucial during crises and natural disasters. Although network-based ECSs have been extensively studied, integrating open-source technologies, such as software-defined wide area networks (SD-WAN) with private long-term evolution (LTE) base stations, is a relatively unexplored domain. This study endeavors to fill this gap by introducing an experimental ECS platform that utilizes a hybrid network, incorporating a VoIP network to enhance open-source and on-premises communications in targeted areas. Our hypothesis posits that a hybrid network architecture, combining SD-WAN and private LTE, can substantially improve the reliability and efficiency of ECSs. Our findings, supported by the open-source OMNeT++ simulator, illuminate the enhanced communication reliability of the network. Moreover, the proposed platform, characterized by autonomous wireless 4G/LTE base stations and an Asterisk VoIP server, demonstrates improved quality of service (QoS) and quality of experience (QoE), with minimal data loss. This research not only has immediate practical applications but also bears significant implications for the development of cost-effective, open-source communication networks, optimized for emergencies, critical infrastructure, and remote areas. [ABSTRACT FROM AUTHOR]

By referring to the service network architecture and interoperation scheme of VoWi-Fi under 4G, the differences of the service network architecture and interoperation scheme of VoWi-Fi under 5G were studied and analyzed.Under the current situation that the network and terminal industry chain didn’t support the interoperability between standalone (SA) and Wi-Fi, a workaround scheme for interoperation in the transitional period was proposed, and the terminal and network side configuration suggestions were given to realize the interoperation between VoWi-Fi and VoLTE based on 5G network to ensure that users were unaware.The feasibility of this scheme was verified by practical tests.It provides reference for the actual deployment of VoWi-Fi.

Abstract4 G mobile networks have evolved to meet the ever-increasing demand and requirements of users. 4 G will provide comprehensive IP solutions, allowing users to access voice, data, and streaming multimedia services at any time, from any location. Nonetheless, this transition will introduce new vulnerabilities and threats to service providers and customers. With the introduction of machine-to-machine (M2M) communication and the Internet of Things (IoT), malicious actors now have more attack ground. Attackers have an easier time sneaking into 4 G networks in developing countries because outdated and unprotected devices are still in use. Many startups and individuals did not invest in protecting their devices, owing to financial constraints and a lack of fundamental cyber security awareness. Because many network devices in developing countries are old and poorly protected, they could serve as a launching pad for perpetrators. This work thoroughly investigates and discusses fundamental security flaws in the 4 G network. These flaws could provide a path for malicious actors. Several factors exist in developing countries that expose them to perpetrators have been explained and elaborated on this work. Additionally, potential solutions to combat these issues are proposed.

By referring to the service network architecture and interoperation scheme of VoWi-Fi under 4G, the differences of the service network architecture and interoperation scheme of VoWi-Fi under 5G were studied and analyzed. Under the current situation that the network and terminal industry chain didn't support the interoperability between standalone (SA) and Wi-Fi, a workaround scheme for interoperation in the transitional period was proposed, and the terminal and network side configuration suggestions were given to realize the interoperation between VoWi-Fi and VoLTE based on 5G network to ensure that users were unaware. The feasibility of this scheme was verified by practical tests. It provides reference for the actual deployment of VoWi-Fi. [ABSTRACT FROM AUTHOR]

Voice over long term evolution (VoLTE) in long term evolution-advanced (LTE-A) is gaining more and more popularity these days. However, the increasing demands of subscribers raise new challenges in wireless network to support large number of concurrent active users while maintaining the desired delay requirements. To realize the issue, this paper proposes an LTE-A capacity or eNodeB (eNB) capacity estimation model, i.e. defined as the number of simultaneous users for location-dependent diverse radio conditions. This proposed model incorporates different bundling mechanisms to utilize the radio resources efficiently. Then, optimal transmission parameters α , α ′ using packet bundling, β , β ′ using transmission time interval (TTI) bundling, and η , η ′ for mixed radio condition is derived to enhance the accommodation of a large number of users within an LTE-A cell. There has been almost no consideration in the existing research on LTE-A capacity estimation based on these aspects. Therefore this paper presents novel algorithms based on the proposed models that enable capacity estimation and optimization under diverse radio conditions. The LTE-A cell capacity obtained using the proposed algorithms can be further used as an important parameter for designing call admission control (CAC) in packet-switched wireless networks. [ABSTRACT FROM AUTHOR]

4 G mobile networks have evolved to meet the ever-increasing demand and requirements of users. 4 G will provide comprehensive IP solutions, allowing users to access voice, data, and streaming multimedia services at any time, from any location. Nonetheless, this transition will introduce new vulnerabilities and threats to service providers and customers. With the introduction of machine-tomachine (M2M) communication and the Internet of Things (IoT), malicious actors now have more attack ground. Attackers have an easier time sneaking into 4 G networks in developing countries because outdated and unprotected devices are still in use. Many startups and individuals did not invest in protecting their devices, owing to financial constraints and a lack of fundamental cyber security awareness. Because many network devices in developing countries are old and poorly protected, they could serve as a launching pad for perpetrators. This work thoroughly investigates and discusses fundamental security flaws in the 4 G network. These flaws could provide a path for malicious actors. Several factors exist in developing countries that expose them to perpetrators have been explained and elaborated on this work. Additionally, potential solutions to combat these issues are proposed. [ABSTRACT FROM AUTHOR]

The most effective automatic speech recognition (ASR) approaches are based on artificial neural networks (ANN). ANNs need to be trained with an adequate amount of matched conditioned data. Therefore, performing training adaptation of an ASR model using augmented data of matched condition as the real environment gives better results for real data. Real-world speech recordings can vary in different acoustic aspects depending on the recording channels and environment such as the Long Term Evolution (LTE) channel of mobile telephones, where data are transmitted with voice over LTE (VoLTE) technology, wireless pin mics in a classroom condition, etc. Acquiring data with such variation is costly. Therefore, we propose training ASR models with simulated augmented data and fine-tune them for domain adaptation using deep neural network (DNN)-based simulated data along with re-recorded data. DNN-based feature transformation creates realistic speech features from recordings of clean conditions. In this research, a comparative investigation is performed for different recording channel adaptation methods for real-world speech recognition. The proposed method yields 27.0% character error rate reduction (CERR) for the DNN–hidden Markov model (DNN-HMM) hybrid ASR approach and 36.4% CERR for the end-to-end ASR approach for the target domain of the LTE channel of telephone speech. [ABSTRACT FROM AUTHOR]

Sharing network infrastructure is carried out by a few network operators in the world and is regarded as an effective means to accelerate the commercial 5G with seamless coverage and user experience guarantees but significantly reduced investment. Voice via IMS has been defined as the voice-bearing solution from 3rd-Generation Partnership Project (3GPP) Release 5. Release 15 pointed out that 5G still adopts the IMS-based voice service architecture. In such a background, and in the process of global 5G network evolution from non-stand-alone (NSA) to stand-alone (SA), how to bear 5G voice services in the sharing network infrastructure has quite a few technical options. This paper investigates the 5G access network sharing technical solutions and presents the voice bearer technology under different new radio (NR) evolution stages. Analysis was performed for the different stages of voice handover. Performance results from field tests are provided to verify the feasibility of the solution, and performance analysis such as end-to-end call setup delay was also carried out. From the theoretical and practical analysis, the voice over long-term evolution (VoLTE) non-back-to-home solution has a relatively short access delay in the NSA sharing stage; EPS fallback based on either handover or redirection introduces a large time delay, so EPS fallback can only be used as a transition solution in the early stage of SA sharing deployment; voice over new radio (VoNR) has the lowest access time delay and the simplest implementation solution, so it is the final voice solution for 5G SA sharing network. The comparison of different voice-bearing solutions in different network development stages provides a reference for countries around the world. [ABSTRACT FROM AUTHOR]

Abstract As the PHY/MAC-layer IR-HARQ and RLC-layer ARQ error recovery procedures, adopted in LTE, may impose additional delay when their code-block retransmissions occur, the arising question is whether these significantly contribute to IP and consequently RTP packet delays, and finally degrade the overall application-layer end-to-end QoE, especially when voice is transmitted over LTE? With this regard, we propose and demonstrate a VoLTE QoS and QoE test procedure based on PHY/MAC/RLC/IP/TCP-UDP/RTP cross-layer protocol analysis and perceptual speech quality QoE measurements. We identified monotonic relationship between the paired observations: QoE and HARQ RTT, i.e. between the PESQ voice quality rating and the IP/RTP packet latency, for given BLER of the received MAC/RLC code-blocks. Specifically, we found out that, for the HARQ RTT value of about 8 ms, only up to 2 HARQ retransmissions (and consequently no RLC-ARQ one) is appropriate during any voice packet, otherwise delay accumulation might not be accordingly “smoothed out” by jitter/playback buffers along the propagation path.

Voice over Long-Term Evolution (VoLTE) is the basis for evolving mobile voice and communication services for packet switched networks. However, noise and delay interfere with voice transmission over wireless channels, resulting in a poor Quality of Service. This paper proposes four improved transmission systems for VoLTE. The first and second proposed schemes take advantage of the varying importance of the bits produced by an internet Low Bitrate Code codec to provide distinct levels of security for them by placing the significant bits on prioritized Quadrature Amplitude Modulation (QAM) bit positions before transmission. The third and fourth proposals replace the traditional QAM constellation by a Statistical QAM (SQAM) arrangement. The third strategy is derived by placing the critical bits on the SQAM arrangement and the non-critical bits onto the traditional QAM configuration. For the last scheme, all the bits are placed on the SQAM map. A comparative study was also carried out using two frequency transformations: Fast Fourier Transform (FFT) and Discrete Wavelet Transform, namely Biorthogonal Wavelet. The proposed approaches demonstrated better performance as well as improved segmented signal-to-noise ratio by up to 4.86 dB. In contrast to the use of FFT, an increased gain of up to 4 dB is observed with DWT together with 16-QAM at a code rate of 1/3. [ABSTRACT FROM AUTHOR]

Covert channels are widely used for secret message transmission on networks, and they are constantly changing and updating to adapt to the new network and communication environment. There are a large number of video packets during VoLTE (Voice over LTE), which can be a suitable carrier for covert channels. In this paper, we design a secure covert storage channel for VoLTE via regulating timestamp of VoLTE packets. First, we analyze the data captured in the real environment and find out two statistical patterns for the timestamp of the video packets. Then, we build the covert channel by modifying timestamp to carry the covert message in the case of maintaining these two patterns. Finally, we simulated the covert channel using the data captured in the real environment. Experimental results show that the covertchannel can communication over VoLTE secretly and robustly with bit-rate up to 120 bit/s, and it is against statistical analysis such as the Kolmogorov-Smirnov(KS) test and linear regression. [ABSTRACT FROM AUTHOR]

The increasing number of Voice over LTE deployments and IP-based voice services raise the demand for their user-centric service quality monitoring. This domain’s leading challenge is measuring user experience quality reliably without performing subjective assessments or applying the standard full-reference objective models. While the former is time- and resource-consuming and primarily executed ad-hoc, the latter depends upon a reference source and processes the voice payload that may offend user privacy. This paper presents a packet-level measurement method (introducing a novel metric set) to objectively assess network and service quality online. It is accomplished without inspecting the voice payload and needing the reference voice sample. The proposal has three contributions: (i) our method focuses on the timeliness of the media traffic. It introduces new performance metrics that describe and measure the service’s time-domain behavior from the voice application viewpoint. (ii) Based on the proposed metrics, we also present a no-reference Quality of Experience (QoE) estimation model. (iii) Additionally, we propose a new method to identify the pace of the speech (slow or dynamic) as long as voice activity detection (VAD) is present between the endpoints. This identification supports the introduced quality model to estimate the perceived quality with higher accuracy. The performance of the proposed model is validated against a full-reference voice quality estimation model called AQuA, using real VoIP traffic (originated in assorted voice samples) in controlled transmission scenarios. [ABSTRACT FROM AUTHOR]

As the PHY/MAC-layer IR-HARQ and RLC-layer ARQ error recovery procedures, adopted in LTE, may impose additional delay when their code-block retransmissions occur, the arising question is whether these significantly contribute to IP and consequently RTP packet delays, and finally degrade the overall application-layer end-to-end QoE, especially when voice is transmitted over LTE? With this regard, we propose and demonstrate a VoLTE QoS and QoE test procedure based on PHY/MAC/RLC/IP/TCP-UDP/RTP cross-layer protocol analysis and perceptual speech quality QoE measurements. We identified monotonic relationship between the paired observations: QoE and HARQ RTT, i.e. between the PESQ voice quality rating and the IP/RTP packet latency, for given BLER of the received MAC/RLC code-blocks. Specifically, we found out that, for the HARQ RTT value of about 8 ms, only up to 2 HARQ retransmissions (and consequently no RLC-ARQ one) is appropriate during any voice packet, otherwise delay accumulation might not be accordingly "smoothed out" by jitter/playback buffers along the propagation path. [ABSTRACT FROM AUTHOR]

In the existing network covert channel research, the transmission of secret messages is one-way, lacking confirmation feedback on whether the secret message is successfully accepted. However, voice over LTE (VoLTE) has real-time interactive features, and the data packets between the sender and the receiver are transmitted in both directions, which facilitates the construction of a two-way covert channel with feedback. Therefore, we propose a two-way VoLTE covert channel adaptive to mobile network environment, which includes a sender-to-receiver covert timing channel that modulates covert message through actively dropping packets during the silence periods and a reverse covert storage channel that hides the acceptance of the covert message as feedback information into the feedback control information field of the real-time transport control protocol (RTCP) packet. The sender evaluates the current attack severity according to the feedback and adjusts the real-time parameters of the covert timing channel to weigh the robustness and other performance, thereby constructing a two-way covert channel adaptive to complex mobile network environments. Experimental results show that this solution can maintain voice quality which is an important performance indicator for VoLTE, while keeping the covert channel undetectable and robust.

Covert channels represent unforeseen communication methods that exploit authorized overt communication as the carrier medium for covert messages. Covert channels can be a secure and effective means of transmitting confidential information hidden in overt traffic. For covert timing channel, the covert message is usually modulated into inter-packet delays (IPDs) of legitimate traffic, which is not suitable for voice over LTE (VoLTE) since the IPDs of VoLTE traffic are fixed to lose the possibility of being modulated. For this reason, we propose a covert channel via adjusting silence periods, which modulates covert message by the postponing or extending silence periods in VoLTE traffic. To keep the robustness, we employ the Gray code to encode the covert message to reduce the impact of packet loss. Moreover, the proposed covert channel enables the tradeoff between the robustness and voice quality which is an important performance indicator for VoLTE. The experiment results show that the proposed covert channel is undetectable by statistical tests and outperforms the other covert channels based on IPDs in terms of robustness.

Abstract Long-term evolution (LTE) is becoming the first choice of mobile network operators (MNOs) when constructing a wireless network infrastructure because of its high data rate, high throughput, and low latency. These significant advancements are necessary for satisfying the delivery of a wide-range of mobile applications and managed network resources. However, deploying a new LTE network or a transition from current legacy cellular networks to LTE can take several years to roll out. In the meantime, working in a heterogeneous wireless communication network looks inevitable. This paper investigates Voice over LTE (VoLTE) Quality of Service (QoS) under a heterogeneous wireless communication scenario. The contributions of this paper are twofold. First, a novel downlink (DL) semi-persistent scheduling scheme is proposed to reduce VoLTE end-to-end delay and increase system capacity. Second, an extensive network simulation model has been designed and implemented to evaluate the proposed scheme. The performance of the proposed scheme is compared with the performance of two relevant and well-known DL packet scheduling methods. The simulation results confirm that the proposed scheme is able to reduce VoLTE end-to-end delay and achieve a better system capacity than current methods, and maintain the desired VoLTE QoS.

With the introduction of 5G New Radio (NR), telecom operators are planning to integrate network elements of NR in different configurations for a phased and overlaid deployment and coexistence with 4G. Third Generation Partnership Project (3GPP) standardizes the deployment operation mode of the next-generation network, viz. working in Stand Alone (SA) NR scenarios and Non-Stand Alone (NSA) NR mode scenarios. As defined in the specification, Option 7 is where UEconnects to 5G Core Network (5GCN) via either 4G enhanced Node B (eNB) cell or 5G next-generation NodeB (gNB) cell. The power consumption for a User Equipment (UE) is dependent on the physical resource allocation strategy in the serving cell. Available procedures of system selection defined in 3GPP are based on measurement of reference signalpower levels and priority criteria as defined in the System Information of the 5G/4G network. In this paper, we have discussed novel protocol and algorithm through which the UE maintains a history of availability of features like Semi-Persistent Scheduling (SPS), Connected Mode Discontinuous Reception (CDRX) and Voice over NR (VoNR) in the serving area of a cell and uses this information later during system reselection evaluation due to mobility. Through our proposed changes, a UE a) gets VoNR service more often and b) conserve more energy when the user activates VoNRservice. We present an analytical model and through simulation show that during VoNR service, power is conserved due to SPS and CDRX on the selected cell.

Tuning cellular network performance against always occurring wireless impairments can dramatically improve reliability to end users. In this paper, we formulate cellular network performance tuning as a reinforcement learning (RL) problem and provide a solution to improve the performance for indoor and outdoor environments. By leveraging the ability of $Q$ -learning to estimate future performance improvement rewards, we propose two algorithms: 1) closed loop power control (PC) for downlink voice over LTE (VoLTE) and 2) self-organizing network (SON) fault management. The VoLTE PC algorithm uses RL to adjust the indoor base station transmit power so that the signal-to-interference plus noise ratio (SINR) of a user equipment (UE) meets the target SINR. It does so without the UE having to send power control requests. The SON fault management algorithm uses RL to improve the performance of an outdoor base station cluster by resolving faults in the network through configuration management. Both algorithms exploit measurements from the connected users, wireless impairments, and relevant configuration parameters to solve a non-convex performance optimization problem using RL. Simulation results show that our proposed RL-based algorithms outperform the industry standards today in realistic cellular communication environments. [ABSTRACT FROM AUTHOR]

With the introduction of 5G New Radio (NR), telecom operators are planning to integrate network elements of NR in different configurations for a phased and overlaid deployment and coexistence with 4G. Third Generation Partnership Project (3GPP) standardizes the deployment operation mode of the next-generation network, viz. working in Stand Alone (SA) NR scenarios and Non-Stand Alone (NSA) NR mode scenarios. As defined in the specification, Option 7 is where UE connects to 5G Core Network (5GCN) via either 4G enhanced Node B (eNB) cell or 5G next-generation NodeB (gNB) cell. The power consumption for a User Equipment (UE) is dependent on the physical resource allocation strategy in the serving cell. Available procedures of system selection defined in 3GPP are based on measurement of reference signal power levels and priority criteria as defined in the System Information of the 5G/4G network. In this paper, we have discussed novel protocol and algorithm through which the UE maintains a history of availability of features like Semi-Persistent Scheduling (SPS), Connected Mode Discontinuous Reception (CDRX) and Voice over NR (VoNR) in the serving area of a cell and uses this information later during system reselection evaluation due to mobility. Through our proposed changes, a UE a) gets VoNR service more often and b) conserve more energy when the user activates VoNR service. We present an analytical model and through simulation show that during VoNR service, power is conserved due to SPS and CDRX on the selected cell. [ABSTRACT FROM AUTHOR]

In this paper, we examine the impact of four voice over long term evolution adaptive multi-rate wideband codec mode-sets on coverage at pedestrian and vehicular speeds. Industry-standardized mean opinion scores were used as a metric for voice quality. Controlled laboratory experiments simulating pedestrian speeds indicated that there was an improvement in voice quality when mode-set eight was employed. At vehicular speeds, mode-set eight outperformed the other mode-sets for path losses less than 130 dB; however, all four mode-sets experienced a significant decline in voice quality when the path loss was greater than 130 dB. Based on the current implementations, there are no significant benefits to lowering the mode-sets or deploying dynamic codec rate adaptation.

With the development of LTE data and VoLTE services,subscribers pay more and more attention to network experience.LTE optimization faces many challenges.Therefore,China Mobile Shandong Corporation made a complete and feasibility solution,which met the requirement of high-speed scene optimization.There were four dimensions in this solution: double layers network deployment,VoLTE optimization of high-speed rail,coordinating optimization in the boundary of high-speed network and normal LTE network,and the exploration and deployment of new functions.After the implementation of the solution,VoLTE coverage rate increases from 87.95% to 91.66%,MOS value upgrades from 3.6 to 4,the ratio of MOS value greater than 3.0 rised from 89.61% to 96.70%.

Firstly,the similarities and differences between the acceptance of the TD-LTE VoLTE wireless network engineering and other wireless network engineering were discussed.Then,referring to the different phases of engineering acceptance,the choice of indexes was analyzed.And finally,by driving tests and comparison research,the values of the index were suggested.

The deployment of VoLTE involves all aspects of the network, among them the construction of IMS core network is more crucial. The IMS networking solutions of different manufacturers' devices after the deployment of VoLTE were studied and many recommendations were proposed, which would provide reference for the deployment of VoLTE commercial network.

The realization to communications services of intelligent vehicle mobile terminal was discussed.Technology solutions of network architecture，signaling procedure，network handover and QoS guarantee were proposed.And the specific technology implementation scheme was proposed.

We consider scheduling and resource allocation in long-term evolution (LTE) networks across voice over the LTE (VoLTE) and best-effort data users. The difference between these two is that VoLTE users get scheduling priority to receive their required quality of service. As we show, strict priority causes data services to suffer. We propose new scheduling and resource allocation algorithms to maximize the sum or proportional fair (PF) throughout amongst data users while meeting VoLTE demands. Essentially, we use VoLTE as an example application with both a guaranteed bit-rate and strict application-specific requirement. We first formulate and solve the frame-level optimization problem for throughput maximization; however, this leads to an integer problem coupled across the LTE transmission time intervals (TTIs). We then propose a TTI-level problem to decouple scheduling across TTIs. Finally, we propose a heuristic scheme, with extremely low complexity. The formulations illustrate the details required to realize resource allocation in an implemented standard. The numerical results show that the performance of the TTI-level scheme is very close to that of the frame-level upper bound. Similarly, the heuristic scheme works well compared to TTI-level optimization and a baseline scheduling algorithm. Finally, we show that our PF optimization retains the high fairness index characterizing PF-scheduling. [ABSTRACT FROM AUTHOR]

The Voice over LTE (VoLTE) service is under deployment at many operators. Although it has great promises—from high service flexibility to previously unseen QoS measures—so far it poses more challenges than expected. The serving architecture is diverse, and the flexible services mean variable use-cases with complex message sequence charts. In order to be able to control the procedures—during deployment as well as during the operation—we need to have proper network and service management in place. Such a management framework includes network and service monitoring tools that help to provide better visibility of the various procedures. For the VoLTE service, both the LTE Evolved Packet Core (EPC) and the IP Multimedia Subsystem (IMS) need to be monitored. Network-wide data capture and analysis for the EPC and the IMS require new processing methods. These would allow operators to correlate control and user plane information of various interfaces and protocols. There are many obstacles to overcome here, including ciphered control messages and global identifiers hidden by temporary ones. This paper presents a system for SIP Call Data Record assembling, shows what kind of key parameters have to be extracted in order to enable expert analysis. After going into the details of messages, transactions, and dialogues, we present Call Data Record assembling methods for various scenarios. Furthermore, we present methods on how to gather cross-correlated data on specific fault management use-cases, particularly for unsuccessful voice calls. [ABSTRACT FROM AUTHOR]

As the final voice solution for LTE,VoLTE has become the key research point of the industry.Several existing voice solutions of LTE user equipment were compared and analyzed in details.Technical advantages and unsolved problems of VoLTE which is based on pure PS network and IMS system were mainly discussed from the prospective of the LTE terminal.The technical characteristics and evolution direction of VoLTE were mentioned in the end.

Long term evolution technology（LTE）is a new generation of wireless communications technology. LTE has experienced a rapid development process since 2010. And by the end of 2013, 260 LTE networks has been launched. Chinese government also issued TD-LTE licenses on Dec. 2013. It was specified that LTE was the hot technology based on current wireless markets and technology development. Current LTE development status and challenge it faced were analyzed. Also the positive impaction to TD-LTE globalization brought by Chinese TD-LTE license issuing was analyzed. Based on the analysis, some perspects on LTE development in future were conducted, especially in 2014.

Mobile network operators are increasingly striving to substitute legacy telecommunication technologies in their networks with the contemporary ones. Modern, future-proof architecture that provides better service quality, requires easier and cheaper maintenance, and consequently brings greater financial benefits is the main driving force for that action. In this moment, Long Term Evolution (LTE) deployment is a goal most mobile network operators are aspiring to. This paper describes presently ongoing changes in the mobile communication networks from the perspective of voice services they provide. Namely, LTE network is, so far, mainly recognized as a 'data oriented' network. Having in mind enormous mobile data traffic increase, deployment of that kind of network is fully understandable and justified. However, voice services are still important part of telecommunications' market offer. So, the above mentioned changes are leading not only toward satisfaction of growing needs regarding mobile data traffic, but also toward utilization of LTE network attributes for the purposes of voice communication. Complete transformation of mobile networks architecture and evolution of traditional voice communication will occur in the process. So far, that evolution has resulted with development of a mechanism know as voice over LTE. However, the mentioned changes are coming gradually and will take a certain time to be fully accomplished. In the meantime, some transition solutions are defined and deployed, in order to enable uninterrupted provisioning of voice services. Their description is included in the paper as well. At the end, relevant forecasts of several network parameters have been discussed. [ABSTRACT FROM AUTHOR]

Long-term evolution (LTE) is becoming the first choice of mobile network operators (MNOs) when constructing a wireless network infrastructure because of its high data rate, high throughput, and low latency. These significant advancements are necessary for satisfying the delivery of a wide-range of mobile applications and managed network resources. However, deploying a new LTE network or a transition from current legacy cellular networks to LTE can take several years to roll out. In the meantime, working in a heterogeneous wireless communication network looks inevitable. This paper investigates Voice over LTE (VoLTE) Quality of Service (QoS) under a heterogeneous wireless communication scenario. The contributions of this paper are twofold. First, a novel downlink (DL) semi-persistent scheduling scheme is proposed to reduce VoLTE end-to-end delay and increase system capacity. Second, an extensive network simulation model has been designed and implemented to evaluate the proposed scheme. The performance of the proposed scheme is compared with the performance of two relevant and well-known DL packet scheduling methods. The simulation results confirm that the proposed scheme is able to reduce VoLTE end-to-end delay and achieve a better system capacity than current methods, and maintain the desired VoLTE QoS. [ABSTRACT FROM AUTHOR]

Voice service is one of the basic services that the mobile internet carrier provides for its users. There are severa1 schemes to carry on the voice service in LTE era. The VoLTE scheme was focused on and had been studied both in theoretica1 and implementation views. Based on the 3GPP standards，the key technologies of VoLTE had been clarified，and the network architecture was also studied. Specifica11y，the interoperability between VoLTE and the 1egacy networks was analyzed to guarantee the continuity of service. Additiona11y，suggestions were given for the VoLTE development and business conducting.