Mitigating X2‐AP interface cost using quantum teleportation

IET NetworksVolume 9, Issue 5 p. 247-254 Research ArticleFree Access Mitigating X2-AP interface cost using quantum teleportation Raad S. Alhumaima, Raad S. Alhumaima Department of Communications, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this authorSaib Thiab Alwan, Corresponding Author Saib Thiab Alwan 1234914@alumni.brunel.ac.uk Department of Materials, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this authorRiyadh Khlf Ahmed, Riyadh Khlf Ahmed Department of Communications, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this author Raad S. Alhumaima, Raad S. Alhumaima Department of Communications, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this authorSaib Thiab Alwan, Corresponding Author Saib Thiab Alwan 1234914@alumni.brunel.ac.uk Department of Materials, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this authorRiyadh Khlf Ahmed, Riyadh Khlf Ahmed Department of Communications, College of Engineering, University of Diyala, Diyala, IraqSearch for more papers by this author First published: 22 September 2020 https://doi.org/10.1049/iet-net.2019.0230Citations: 1AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract Many problems in cellular communications cannot be solved classically. Due to its robustness, quantum computing can enrich the classical with other dimensions, security and cryptic-natured. However, the awareness about how to fully bridge the classical and quantum communications is not fully realised. In other words, the quantum phenomena are not totally utilised within the classical dimension. This work rather discusses directions and evaluations for future quantum solutions to traditional cloud mobile networks. Particularly, using quantum correlation phenomena to enhance the performance of X2 application protocol (X2-AP) by reducing the signalling overhead regarding the delay and power consumption that classical cloud encounter. Through modelling the latency of both paradigms using 'MATLAB', this work promises a delay reduction when adapting quantum method into the cloud. This study also models the power consumption and energy efficiency of traditional and quantum-based cloud networks. This work also shows, via modelling the power consumption, that installing a quantum-based paradigm is not a power costly method; rather, it shows identical power and energy efficiency figures with a possibility of improvement. 1 Introduction Information and communications technology (ICT) section consumes about 0.5% of power [1, 2 ], such percentage is going to impact the percentage of CO2 emissions that is harmful to the environment. This was originated from the higher data rates required to serve an increasing number of users (UEs). The number of communication networks' UEs is rapidly increasing with time, which urged the mobile operators to deploy more base stations, varied amongst types such as macro, micro, pico, or a combination of two or more base stations that share the same area such as a heterogeneous network. However, the more number of base stations leads to power consumption rising. Hence, new methods, designs, techniques and innovations are substantial. Mobile networks consume 0.5% out of global energy consumption [3 ]. Due to demanding higher bandwidth and data rates by nowadays communications, the network vendors and operators installed an increased number of mobile base stations, which require more power to operate them. The considerable amount of this power is directed to achieve the necessary control plane and signalling process. The higher number of network UEs indicates increasing at such cost while providing extended protocols and interfaces. Hence, re-design the current network architecture can help to override these network inefficiencies [4 ]. The increasing number of network UEs demand higher bandwidth, low latency, low power consumption and efficient resources allocation. As far as the traditional or classical communications are concerned, enhancing 5G metrics reaches a definitive limit. For example, a reduction in the transistor's size in Moore's law will be unachievable in future due to limitations of manufacturing. Similarly, the number of industrial transistors a circuit can hold doubles every 2 years; this rule runs to its limit too. Likewise, the power consumption and processing delay of the electronic devices have a limit. There are many suggested solutions that are proposed to solve the previously mentioned aspects. On the system level, the power consumption of traditional mobile networks is reduced by suggesting cloud radio access networks [5 ]. The latter power consumption, in turn, is further reduced by virtualising the baseband (BB) units of the cloud centre in [6 ]. There are additional suggestions that are proposed; each solves a particular problem at a time, such as a software-defined network that enhanced the scalability and management issues and unified the control plane of the coming networks [7 ]. In addition, self-organising the networks automates their configuration and predicts the futuristic solutions that optimise their operations [8 ]. Furthermore, several works have been done to optimise the available resources blocks of available bandwidth, such as in [9, 10 ]. However, optimising these resources can no longer enhance the spectral efficiency due to the stingy number of resource blocks of the available bandwidth [11 ]. Moreover, these solutions have an undesirable cost varies amongst increasing the power consumption, delay or complexity. Hence, more efficient technologies have to be adapted to overcome the struggles of classical communications. This solution is by employing quantum mechanics, which represents an incredible and reliable way to accomplish the requirements beyond the current generation. Quantum computing gathers physical principals and quantum mechanics to offer solutions for problems usually; these problems are hard to solve by using classical methods. For example, developing more secure communications using entanglement phenomena [12 ], more advanced quantum oriented resources allocation that encode the classical bit into quantum photon states to offer more bandwidth, using quantum key distribution to offer robust security in Wi-Fi networks [13 ], and so on. Generally, the literature that discusses quantum-classical adaptation is in the early stages and not satisfying. Moreover, the research is rare in regards to adapting quantum methods into mobile communications. This is because quantum computing domain itself is incomplete. In addition, the behaviours of classical and quantum are essentially different. Optical communications technology has involved many quantum characteristics represented by optical fibre channel, laser source to generate the photons, and detecting the light at the receiver side. However, out of two features of the photon, only one, wave property is utilised and demonstrated within the classical communication context. Simultaneously, the photon behaves both wave and particle properties based on the way a photon is measured and manipulated. In other words, if a bit is symbolised by 0 or 1 in the classical domain, it will be represented by and states with a possibility of jointly being 0 and 1, and called a quantum bit (qubit). Recently, the applications and advances of quantum computing are spreading widely, such as quantum entanglement [14 ], quantum routing [15 ], quantum repeating [16 ], quantum relay and encoder/decoder [17 ], quantum synchronisation [18 ], quantum memory [19 ] and quantum cryptography [20 ]. Nevertheless, such technologies were only limited to the quantum domain, and no further investigations were considered regarding utilising them in the classical world. Accordingly, this paper contributed to offering to employ quantum into classical communications: We used the term classical to indicate the non-quantum technologies/paradigms, furthermore, within the classical domain, we used the term traditional to present the non-cloud paradigms. In the quantum domain, the quantum-based cloud refers to the adaptation between classical cloud networks and quantum technologies. 1.1 Contributions Quantum entanglement phenomena are used to mitigate the cost of signalling originated from the handover process of classical cloud communication. A hybrid paradigm is proposed where traditional and quantum networks are combined. In which, classical bits of a particular UE are used to drive a laser, the laser then pumps a non-linear crystal, more than one entangled photons are generated. These photons are distributed using an optical fibre channel to the remote radio unit (RU). At the RU, the classical bits are retrieved. These photons are utilised to provide 'off the shelf' duplicate bits, generated with no additional cost. When a UE moves to the neighbour RU, its information is served instantly using these duplicate bits. In this situation, the need for an X2-AP application protocol for handover signalling is mitigated. Reducing the amount of signalling of the X2-AP protocol has relieved the latency. The latter is originated due to transferring UE status while moving between the RUs. To evaluate the delay, analysing and modelling both, the State-of-the-Art (SotA) and quantum-based handover delays have been achieved. Time delay saving can inherit additional power trade-offs. Hence, a simplified, parameterised power model that measures the consumption of both traditional and quantum networks is proposed. The quantum-based X2-AP is compared with the SotA process in terms of power consumption, delay and energy efficiency. The originated cost is also discussed. This work also offers a generalised platform to test the power gain and consumption, energy efficiency, channel capacity and time delay for the futuristic solutions which are proposed to enhance the quantum communications. 2 Quantum fundamentals The analogue classical bit in quantum mechanics context is called a qubit, denoted as ( ) and represented by two states system, where or , where and denote the probability amplitudes for a qubit to be in a superposition of 0 or 1, respectively. Through and , it is inaccessible to recognise where the qubit is in the state or [21 ]. Any two-state system is capable of encoding the qubit, such as electrons spin, nuclei spin and photon polarisations. Nevertheless, in the communications field, the photons are ideal to symbolise the qubits as they hold reducible interaction amongst other particles and amongst each other, which achieves the maximum coherency. Therefore, qubits can preserve their polarisation states for extended long periods of time with the speed of light [22 ]. Once the qubit is generated, it holds no specific polarisation state even if it is orthogonal with its twin photons, however, it breakdowns to its final state if a measurement has been achieved, i.e. or . Subsequently, the state can be determined via an absolute value for its probability amplitude, which produces the probability. Which means, the state has been perceived by . In addition, the state has been displayed by . The combination of such probabilities yields is equivalent to 1 [23 ]. Since the possibility of a qubit is new to the old-style communication, the numerical portrayal and the physical representation of the state polarisation are explained in some examples. The photon is displaced with the probabilities' amplitudes The qBit can be composed as , where the and represent the state for a photon to be vertical or horizontal polarisation, respectively. The probability amplitude a photon is passing a horizontal polariser is given as follows: which is additionally can be composed as . The former state has the likelihood of 1, and the second state is 0. Thereafter, the case of the vertical polarisation is displayed as follows: So to the above case can also be composed as as the likelihood of the subsequent state is 1, while the principal state is 0. Another express that can be delivered is the point at which the horizontal or vertical goes through +45 polariser; this state can be spoken to as , where its probability amplitude can be given as follows: This means the photon's probability to be vertical becomes , whereas the horizontal case is . In the event of −45 polarisation, it will be equivalent to . The probability of such a case can be given as follows: This also indicates that the horizontal photon's probability is , and the vertical is . In such cases, the intensity of the photons pass the −45 or 45 polarisers will be and less than coming light. If Hermitian operator is applied to these cases, the eigenvalue is produced for and for , respectively. Herein, we further explain what does it mean to speak of a Hermitian operator, eigenvector or eigenvalue. Assume the vertical polariser is a device with indicators attached to it, red and green. If a light passes through such device, the green light will be lit if it is vertical, otherwise the light is horizontally polarised with the red light becomes on. The light here symbolises an eigenvalue as it is impossible to have a piece of knowledge about its state without performing the measurement. Therefore, the measurement's result will be called eigenvalue, symbolised as , and holds the values −1 or +1. On the other side, the photon's state can be called eigenvector, whereas the device, the polariser, denotes a Hermitian operator. It is good mentioning that directly measuring the photon's state is intractable, rather, the measurement's result ( ) be looked at to know the state, where , and s denotes the index of the state. More information can be found in [24 ]. As mentioned earlier, if the light comes with an angle, it will hold intensity equivalent to , and is the angle of the polariser. This means a photon holds polarisation has probability amplitudes and . To generalise this concept, a photon with angle polarisation passes through polariser; then its probability can be given as . If , then such probability yields , as mentioned earlier. 2.1 Quantum entanglement The quantum mechanics hold unique behaviours; the most interesting one is named quantum correlation, teleportation or entanglement. This phenomenon allows passing the photon state amongst several and distant sites immediately [25 ]. A process called spontaneous down-conversion is used to generate the correlated photons, in which, strong beam with a high frequency of laser non-linearly interacts with the non-linear crystal. In 1935 this theory was discovered by Einstein, Podolsky and Rosen scientists, named as the EPR paradox. They had considered such behaviour to be impossible because the real facts are violated; it was also called as spooky action by Einstein. This was because the correlation amongst the photons takes zero time, which is violating the limit of the speed of light, via ambiguous wave functions. However, this phenomenon is practically proved in several researches, as in [26, 27 ]. This means it is possible one traditional bit drives a laser to pump a crystal and generate several photons. In other words, it allows the transmitter to send pairs of bits by using individual classical bit without complicating the system by using the power-consuming encoding techniques. In addition, the generated photons are inherently secured and no further security techniques are required because the generated photons' states are in a superposition, for instance, a vertical and horizontal state. In the receiving side, a polariser is used to collapse the photons and obtaining one of its two states. One characteristic of entanglement is when the photon is determined; the second photon collapses to its orthogonal state immediately, this allows the information about the second state to be known by the first. To conclude, two amazing properties of entanglement can use in the field of classical communication, generating many photons by using one traditional bit, and these photons are totally correlated by a mysterious wave function. More information about the mathematical representation of entangled photons can be found in [28 ]. 3 Quantum cloud networks Mobile clouds are proposed to hold onto the increment in the traffic volume, just as giving improvement to the UE's quality of experience and service [29 ]. The issue with cloud radio access is that the network's UE is demanded to interface with the cloud centre to handle its information, then the data centre sends these processed data to the UE through the RU. Subsequently, the network delay is increased because the distances to the UEs are increased when compared to the traditional networks. In the latter, the UEs are served by the RUs, which hold distances closest to UEs than the cloud centre Another latency occurs as a reason for control plane communications. If there should arise an occurrence of handover, there will be numerous packets exchange among the UEs, destination BB, source BB, serving gateway, packets gateways and mobility management units. This matter builds the expense of latency and power utilisation because of increased signalling and complexity. Thus, our method aims that the correlated photons can be used to fill in as primary handover signals among the associated RUs to reduce such cost. The pool sends the handled information to the RUs, at that point the RUs send these to the network UEs. In the event that the correlated photons are produced at the pool and sent to the associated RUs. It is possible to utilise these distinguishable photons at the RU and retrieve the information. Once photons are sent to their allocated RUs to be detected, now it is easy to find the photons' states at each other RU instantly, offering relaxed inter or intra tier signalling as the pool only demanded to speculate one of the states so as the other states are known. This research considers this hidden channel amongst entangled photons as well as generating several classical bits using a single bit. 4 Related works The work in [30 ] has discussed the adaptation cost of using quantum in classical communications. In [31 ], the technical dimension of quantum computing based systems has been presented, such as quantum memory, quantum gates, quantum controlling and quantum error correction. In [32, 33 ], the channel entropy of the quantum channel has been studied. In [22 ], quantum repeaters have been presented to mitigate the probability of errors via modelling the channel capacity. In [34 ], a satellite has been utilised to exchange entangled photons over 100 km distance. This advocate with the possibility of adapting the classical communications based entanglement system. A model is proposed in [35 ] to provide a solution by utilising the security characteristic of entanglement in quantum-based internet networking, similarly in [36 ]. The authors of [37 ] proposed a multilayer procedure that optimises the quantum Internet-based network, such technique limits the processing time of node's quantum memory, augments the links' throughput, and decreases the number of those connections. In [38 ], the entanglement theory has been used in providing security of the networks by allowing quantum bits based key distribution. The researchers of [39 ] have used the free space to experimentally distribute the entangled photons over a distance of 13.5 km. After this long distance, the authors showed the entangled pairs can always survive. Classical data are sent utilising quantum teleportation channel amongst parties, the traditional and quantum are altogether assessed in [40 ]. This research additionally proposed a convention for such kind of interchanges. In [41 ], teleported photon sets are utilised to improve the capacity limit of the network via utilising the teleportation connection conduct to encode progressively amount of bits, utilising optical fibre. The authors of [12 ] have demonstrated that traditional and quantum data can impart without sharing a reference signal by utilising the relationship of the teleportation photons. Furthermore, Table 1 presents up to date protocols and advances regarding quantum oriented communications. Table 1. Related literature Research Method Applications [42 ] private quantum communication mobile communications [43 ] quantum networking wireless communications [44 ] super-dense coding decoding the quantum bit [45 ] telepathy channel security [46 ] concentrating entanglement transformations [47, 48 ] channel capacity quantum channels [49 ] unique numbers generation quantum coding [50 ] key distribution quantum security [51 ] optical communications communication protocols [52 ] entanglement quantum broadcasting [53 ] compression coding [54 ] non-cloning ciphering 5 Quantum performance 5.1 Quantum handover One of the fundamental issues in traditional systems is to confine the overhead in the control part. An amplified amount of control plane signalling causes more power consumption, complexity and latency [55 ]. The handover procedure devours significant measure of energy and causes more delay that partakes to call drop and non-consistent UE's conveyance starting with one RU then onto the next. Before expounding on the proposed arrangement, it merits clarifying the conventional method for moving the UE's starting with one RU then onto the next, as pursues: The UE reports its serving RU about the handover request to the destination RU by inspecting the maximum power received from all conceivable objective RUs via RRC estimation control signals. The source RU checks the UE's report via an RRC control signal. In this way, the RU with a higher power is chosen as target RU. The source RU sends a handover request to the target RU to pass the required data (e.g. RU information, UE context, Security context, resource blocks mapping) to prepare for the handover process. The target RU checks the resource availability and reserves the required resources, then sends an acknowledgement for the former handover request; after that, the handover decision occurs. Meanwhile, the UE attempts accessing the target RU, in the event that it prevails, it sends the 'RRC connection configuration complete' message to the target RU. Subsequently, the latter sends a message to the MME to inform that the UE has changed his RU. The MME sends the UE's information to the SGW and PGW, including his current location. After, the SGW transmits downlink packets to target RU instead of the source RU, and acknowledges the MME. Finally, the target RU requests the source RU to release the UE's resources. With this, the handover process has been completed. It merits referencing the RUs have no control to handle the handover process; rather, the BBs are altogether liable for such method in the pool. The quantum-based technique will have favourable circumstances over classical handover, as pursues Let's expect that RU1 has been served by BB1 and RU2 is served by BB2, as shown in Fig. 1. In spite of the fact that the UE of RU1 made a move to RU2, despite everything, it can still be served by its serving (BB1) as there (at least two) photons (converted to traditional bits at the RU) are produced from the one bit of UE's information. Subsequently, its data are duplicated in a split second to the objective RU2; this circumstance can spare power and time in the pool. Fig. 1Open in figure viewerPowerPoint Quantum handover process architecture Fig. 2Open in figure viewerPowerPoint Flow chart comparison between, (left) classical and (right) quantum handover process This implies the moving UE to the objective RU2 can even now be served by BB1, for example the objective BB is not taking part in serving the coming UE for a reason. In addition, no extra control signalling is demanded with the prerequisite of UE's status move, which is important for refreshing at which RU the UE are existed right now. Creating a few photons that in the end are meant classical bits implies the cloud data are in a split received by entanglement situated RUs. This makes refreshing a building up new administrations is a lot simpler and quicker than classical strategy, at which, each RU is assigned a distinctive set of data. Offering channels that are free of interference via utilising optical fibres to move the photons among the RUs and cloud centre. The investigations have demonstrated the X2-AP protocol is confronting an enlarged failure in the classical communications; such disappointment is identified with unsteadiness and scalability [56 ]. Besides, this interface should be updated in all BBs to the most up to date of its standard; such issue is tedious and expensive [57 ]. Thus, entanglement can be a legitimate solution. Due to sparing more than entangled photons, the handover process started even before the handover is requested, as shown in Fig. 2. Classically, within the network architecture, some of the BBs do not have X2-AP interface among them; in this case, S1 protocol is the substitution. Two BBs are associated with the MME to handle the handover. In this situation, the entanglement strategy speaks to an ideal substitution of X2 and S1 to accomplish the handover. 5.2 Quantum efficiency The equation of the traditional entropy is characterised as an average measure of data to be received from a data source. It is the aggregate of the probabilities of the created symbols, for example , where E means the quantity of symbols, and is the likelihood of symbol to be received. For instance, the two symbols coin entropy, each symbol is 0.5 likelihood, yields 1 bit of data. The quantum has a similar representative to traditional entropy, which is defined by von Neumann, it very well may be given as , where S is the total amount of quantum states, and denotes their eigenvalue [58 ]. Since we are keen on measuring the quantum energy efficiency, we changed the entropy formula in regards to the power received at the RU, alongside the eigenvalues. We suggested the power of each photon state is , henceforth, the entropy of such a system is given as , where , denotes the capacity. Along these lines, the quantum received energy efficiency ( ) of the UE can be formulated as follows: (1) The denote the signal-to-noise and interference rate, while BW represents the bandwidth. In addition, denotes the transmitted power from the r th RU to the ue th UE, N symbolises the received AWGN, and is the channel gain of ue th UE and r th RU. Furthermore, speaks for the path loss between ue th UE and RU r, is the path loss factor. Moreover, represents the distance between ue th UE and r th RU, and given as , where , , , symbolises the axes of x and y for the UEs and RUs, respectively. The denotes the network power consumption. It is great referencing that the receiving power from the pool by r th RU at every state of the photons is related restricted by its likelihood , and given as follows: (2) where pa indicates the received power intensification in the RU. Moreover, indicate the attenuation and power of the state s while venturing out to the RU r serving ue th UE. 5.3 Quantum consumption If we accept the network's power consumption is indicated as . The power consumption of the traditional cloud is , and the power consumption of the quantum side is , where (3) The cloud contains an amount of servers for processing the baseband signals. The server power consumption is meant as , where , and Y demonstrates the quantity of BB servers. Then again, the quantum side within the pool ( ) comprises the power consumption of the laser ( ) and power consumption of the detector ( ). Thus, the power consumption of the entanglement part is formulated as , where Dr and Lr mean the quantity of photon detectors and lasers, respectively. It merits referencing that optical units inside the entanglement do not consume power, for example, the generation crystal, the laser splitter, the lenses and so forth. The is likewise exposed to the impacts of different losses found inside the server, for example, cooling, AC and DC. These are straight scaled with other units' power consumption and estimated by utilising the factors ( , , ) to speak to AC, DC and cooling. Progressively, the complete power consumption of quantum network ( ) can be summed (4) The other piece of demonstrating is identified with the radio unit power consumption ( ). The radio unit is likewise built of several units; it is displayed as (5) where denotes the power consumption of the amplifier, while is the amplifier's efficiency, and represents the radio-frequency unit power consumption. Along these lines, the complete power consumption can be given by combining the classical, quantum and radio unit part, as pursues (6) 5.4 Delay performance In the cloud, the total handover delay is somehow less than traditional network because the BBs have been situated in one place. In spite of the fact that sets of millisecond time delay appear to be inconsequential. However, in perspective on mobile networks, such latency is viewed a