The softwarization and virtualization of network functions have enabled better flexibility and manageability in mobile communication systems today. However, considering the slowdown of Moore's law, it would be critical to reduce the cost of providing data plane services in the 6G era. In this paper, we argue that by leveraging programmable network devices such as Smart Network Interface Cards (SmartNICs) and programmable switches, we can offload custom network functionalities instead of using expensive host CPU resources for data plane operations. We propose S-Core, a scalable systems design for mobile packet core harnessing network data plane offloading. S-Core operates on top of multiple heterogeneous network devices, where heavy-hitter session rules can be dynamically placed in response to varying network traffic. Based on our prototype implementation, we argue that the use of programmable network devices will enable lessened CPU load, reduced latency, and improved energy efficiency in the next-gen communication systems.

The 5G Core networks (5GC) are witnessing a drastic increase in signaling traffic volume due to flat Service Based Architecture (SBA) with “any to any” Network Function (NF) communication. The increased signaling, if not managed properly, may hamper the timely delivery of control messages, degrading the user's quality of experience. The underlying reason for increased 5GC signaling is high inter-dependencies between NFs that result in long, complex, and sequential system procedures. Moreover, system procedures are not optimally designed for cloud-native SBA based 5GC. This paper analyzes the system procedures for the current 5G network in order to decouple the sequential procedures into small and independent transactions. Once decoupled, the control messages can be executed in parallel, significantly reducing the procedure completion time and improving compute resource utilization. Although we decouple a few control messages in 5G registration procedure, we are limited by the design of NFs, which introduces inter- Nfcoupling. Thus, architectural changes are imperative to enable loose coupling between NFs. We present an end-to-end SBA based network for 6G and propose enhanced system procedures that allow parallel execution of control messages. We perform simulations for the modified registration procedures, demonstrating approximately 13 % and 24 % decrease in procedure completion time for 5G and 6G, respectively.

Trustworthiness, privacy and resilience are expected to be essential requirements of 6G on top of various other conventional performance requirements such as data rate and latency. Primary authentication is a key procedure for initiating secure communication between User Equipment (UE) and Home Network (HN) in 3rd Generation Partnership Project (3GPP). However, primary authentication mechanisms used in 5G are vulnerable against quantum machines, replay attacks, and rouge base-station. To protect against these threats, we propose beyond 5G and 6G primary authentication methods to adapt hybrid mechanisms which combines Post Quantum Cryptography (PQC) and existing asymmetric algorithm with Perfect Forward Secrecy (PFS) guarantee. We evaluate proposed methods using our in-house developed Simulator “WirelessPQCSim.” Our proposed Hybrid mechanisms provide enhanced security without additional CPU overhead with respect to exiting 5G system. We also achieved up to 6.7x speed-up for PQC-based methods with respect to 5G system and provide low latency which is one of the KPI for 6G system.

In this paper, we propose a new user-plane (UP) network architecture for 6G cellular networks, where there is no distinction between radio access network (RAN) and core network (CN). We define a new network function (NF), called merged-UP (M-UP), where the UP functions of both RAN and CN sides are merged, thus enabling efficient protocol operations. We also propose an IP flow-based radio quality-of-service (QoS) control scheme to support 6G services with diverse QoS requirements. Based on our network testbed system, we show that the proposed architecture improves the system performance in terms of packet processing load and maximum throughput.

Network virtualization and cloudification are being actively introduced into mobile networks, but the current control-plane (CP) architecture, which distinguishes radio access network (RAN) from core network (CN), is inefficient in fully utilizing the flexibility provided by such technologies. In this paper, we propose a novel CP architecture, which is based on service-based interface (SBI) throughout the network without distinction between RAN and CN, thus reducing the delay and overhead of control signaling. The proposed architecture not only reduces the completion time and amount of signaling of the control procedures by up to 27% and 45%, respectively, but also provides a cloud-friendly environment in which slices and sub-networks with various characteristics can be easily operated by configuring the CP at will.

Near Field Communication (NFC) is a wireless communication technology using 13.56 MHz to support 2-way communications between two devices within ~10 cm. Such a short communication range may be considered as a shortcoming, but at the same time, this enables a secure data transfer within the connectivity region when compared to Bluetooth Low Energy (BLE) or Wi-Fi. Accordingly, NFC can be optionally utilized when secure data are transmitted in various services and applications focusing on ID validation. This demo presents a proof-of-concept for an alternative packet transmission method for achieving secure data exchange based on IP-over-NFC technology. For realizing this, there are a number of technical challenges. Utmost, the current NFC Linux kernel driver requires updates for supporting network-layer functionalities. Using such implementations, this demo demonstrates the procedures of transmitting secure data using NFC, while normal packet transmissions occur over WiFi simultaneously.

Femtocell base station (BS) is a low-power, low-price BS based on the cellular communication technology. It is expected to become a cost-effective solution for improving the communication performance of indoor users, whose traffic demands are large in general. We propose long-term parameter optimization schemes for open and hybrid femtocells, which maximize the average throughput of macrocell users by offloading the macro users' downlink traffic to femtocells. To achieve this goal, load balancing between femtocells and macrocells is needed, and hence, we jointly optimize the ratio of dedicated resources for femtocells as well as the femtocell service area in open access femtocell networks by numerical analysis. Then, we extend our algorithm to hybrid access femtocells, where some intra-femtocell resources are dedicated only for femtocell owners, while remaining resources are shared with foreign macrocell users. Our evaluation results show that the proposed parameter optimization schemes significantly enhance the performance of macrocell users because of the large offloading gain. The benefits provided to femtocell users are also adaptively maintained according to the femtocell users' requirements. The results in this paper also provide insights about the situations where femtocell deployment on dedicated channels is preferred to the cochannel deployment.

Femtocell is a cost-effective solution to both soaring wireless data traffic and coverage hole problems. Along with technical issues, the economic benefit which Wireless Service Providers (WSPs) and mobile users get from the femtocell service is a key to successful adoption of femtocell technology. In this paper, we study pricing issues for femtocell service using game theoretic approach. We propose a realistic and detailed pricing framework, and model the interaction between a monopolist WSP and users by a leader-follower game. We also model the competition between two WSPs in a duopoly market at the adoption of femtocell service by a non-cooperative simultaneous game. The competition between femtocells and repeaters is also considered using the same pricing framework. Analysis results present important factors and pricing strategies for economic success of femtocell technology.

Femtocell base station (BS) is a low-power, low-price BS based on cellular communication technology. It is expected to become a cost-effective solution for improving the communication performance of indoor users, whose traffic demands are large in general. There are mainly two access strategies for femtocell, i.e., closed and open access strategies. While it has been known that open access femtocells contribute more to enhancing the system-wide performance than closed access femtocells, the performance of open access femtocell owners can be potentially degraded when sharing their BSs with other macrocell users. To prevent this potential problem, we develop a load balancing scheme which maximizes the average throughput of macrocell users while guaranteeing some degree of benefits to femtocell owners. To achieve this goal, we jointly optimize the ratio of dedicated resources for femtocells as well as the femtocell service area via an analytic model, which proves that the optimization is a convex optimization problem in the typical environments. Our analysis and simulation results show that the proposed load balancing scheme significantly enhances the system-wide performance.

Self-organizing network (SON), which is an essential technology of future radio networks, is proposed in the 3GPP Long Term Evolution (LTE) specification as a usage case. In this paper, we focus on user equipment (UE)'s power control considering interference mitigation and retransmission constraints especially for physical random access channel (PRACH) of LTE. When a UE initially accesses an evolved-NodeB (eNB), it sends a preamble with an initial access level, and raises the power by a fixed step whenever the preamble was not detected by the eNB. We present an analysis and simulation to study the tradeoff relationship between inter-cell interference and retransmission according to the PRACH power setting, i.e., the initial target received power and power ramping step, assuming Rayleigh fading channels. Furthermore, we propose an algorithm tracing the optimal power setting that minimizes the resource wastage of the cell in consideration and its adjacent cells satisfying the constraint of retransmission and failure probability bound.

A Tactical Information Communication Network (TICN) enables communication among military entities during warfare. In a TICN, base stations (BSs) are required to move along with mobile devices in order to provide the communication wherever they are. This type of BS is referred to as Mobile Base Station (MBS). The backhaual of an MBS is composed of a wireless communication link so that the performance of a TICN can be limited by the unstable backhaul link capacity. In this paper, we propose load balancing algorithms considering the capacity of backhaul links in a TICN. Association control based load balancing algorithms and transmit power control based load balancing algorithms are proposed and analyzed. The simulation results demonstrate that the proposed algorithms improve the system performance of a TICN by reducing the outage rate significantly.

In cellular systems, a handoff process is defined to transfer an active call of an MS from one cell to another in order to provide a seamless service to this MS. Generally, a handoff decision is made based on received signal strength (RSS) values from the current base station (BS) and neighboring BSs. In the traditional mobile communication systems, measured RSS directly indicates the quality of the communication link because the same transmission/reception technologies are utilized for all devices. However, emerging cellular systems are defined to utilize various transmission/reception technologies, e.g., Multiple-Input Multiple-Output (MIMO), and different BSs and MSs might be capable of different technologies. Because RSSs do not indicate the quality of the link directly in such cases, we here propose to use a new metric, called effective SNR for handoff decision and show that the proposed scheme significantly improves the system performance when heterogeneous types of devices co-exist in the network.

In this paper, we propose a distributed load balancing using association control, especially for Tactical Information Communication Networks (TICNs). We develop a scheme for effectively balancing the load at the Base Stations (BSs), where a BS's load represents the amount of resources utilized by a BS, thus minimizing the blocking probability as well as the transmission failure probability. In order to make it more suitable to the military environment, we develop the proposed scheme in a completely distributed manner. Extensive simulations are performed and the proposed scheme is found to outperform the association schemes existing in the literature.

One-way delay is an important metric to evaluate the performance of communication networks. In this paper, we analyze the one-way delay performance of the commercial WiBro networks based on the traffic measurement. In measurements, much large delay is observed in the uplink than downlink, and we find that such asymmetry due mainly to the impact of the uplink bandwidth request mechanism. Due to this large uplink delay, the performance of commercial IEEE 802.16e service can be severely degraded. We also discuss some possible solutions to ameliorate this problem.

Femto BS (base station) is emerging as a key technology to secure the coverage and capacity in indoor environments. However, since the existing macrocell network is overlaid on femtocell networks utilizing the same set of frequency channels, femtocell networks can originate severe co-channel interference to the macrocell network unless the femtocell network is carefully configured. Therefore, according to a desired network-wide objective, we optimize the femtocell network with constraints such that the service connectivity with a femto BS is secured in the target indoor area while the signal emitted out of the building, playing as interference to the outdoor users, should be controlled with an appropriate strength in order not to interrupt the communication between macro BS and outdoor users. Each optimization problem is formulated as a mixed integer programming, and as the results, we obtain not only the transmit power and operational frequency channel of each femto BS, but also the optimal femto BS-to-user association pair at each geographical position.

WiBro(Wireless Broadband) is a Korean version of Mobile WiMAX/IEEE 802.16e system, which is designed for mobile broadband wireless access. Being a subset of IEEE 802.16e, WiBro employs orthogonal frequency division multiple access (OFDMA) and time division duplexing (TDD) schemes operating at 2.3 GHz bands. In mid 2006, the world first commercial Mobile WiMAX service, based on WiBro specification, started in Seoul, Korea. In this paper, we analyze the performance of commercial WiBro networks through traffic measurements. Many experiments are conducted in the various environments. We analyze the link capacity when the user datagram protocol (UDP) packets from multiple users fully utilize wireless links. We also analyze goodput performance with transmission control protocol (TCP) as well as round trip time performance. The measured performances are compared with those of HSDPA (High-Speed Downlink Packet Access) which is a competing system of Mobile WiMAX. We found that the RTTs of WiBro and HSDPA are very large compared with conventional data networks, e.g., Ethernet or Wireless LANs. Furthermore, it is shown that the user-perceived performance is limited by such long round trip times when TCP is utilized. It motivates us to improve round trip time performance of WiBro system. Finally, we analyze the VoIP performance and the performance when the user moves around the whole city.

In the wireless data systems, automatic repeatrequest (ARQ) is used in order to reliably deliver packets to the upper layer while hybrid ARQ (HARQ) intends to improve the reliability over the air through the combination with other transmission techniques, e.g., modulation and channel coding. While the two functions are complementary to each other, it has been typically recognized as if they work independently at their corresponding layer. However, we note that the retransmission via ARQ is correlated with whether HARQ eventually delivers a packet successfully within a retransmission limit. Capturing this observation, we in this paper introduce a new ARQ feedback scheme called Cross-Layer ARQ (CL-ARQ). CL-ARQ makes use of the acknowledgement of HARQ internally. CL-ARQ not only allows ARQ to operate without explicit acknowledgement, but also improves the reliability combined with existing ARQ protocols. Especially, when the entities in charge of HARQ and ARQ are located far apart geographically, we show that CL-ARQ remarkably outperforms other schemes. Additionally, CL-ARQ is shown to resolve the stall problem, which occurs when the link capacity can not be fully utilized due to the limitation of ARQ window size. We evaluate the performance of CL-ARQ via both analysis and simulations.