Analysis of Coexistence between IEEE , BLE and IEEE in the 2.4 GHz ISM Band

Transcription

1 Analysis of Coexistence between IEEE , BLE and IEEE 82. in the 2.4 GHz ISM Band Radhakishnan Nataajan, Pouia Zand, Majid Nabi Holst I. I NTRODUCTION In ecent yeas, the emegence of IoT has led to an explosive gowth in the numbe of smat wieless devices. Many IoT applications have thei own Quality-of-Sevice (QoS) equiements. In esponse, vaious low-powe wieless technologies such as IEEE [] and BLE [2] have been developed and adopted widely. The globally allowable opeational band fo these technologies is the unlicensed 2.4 GHz ISM band as shown in Fig., which is also used by othe wieless technologies such as IEEE 82. [3]. The esult is coss-technology intefeence that affects the QoS of the netwok, paticulaly its eliability and latency, which may in tun lead to application failue. Achieving coexistence of diffeent wieless technologies is theefoe a majo challenge in designing an IoT netwok. Coexistence between diffeent wieless technologies can be classified into thee domains: space, time and fequency. Coexistence can thus be achieved by meeting one o moe of the following conditions: ) Adequate spacing between the netwoks 2) Contolled time-shaing of the channel 3) Adequate fequency sepaation between the netwoks Coexistence mechanisms can be classified into two categoies: non-coopeative and coopeative, depending on whethe the involved netwoks opeate independently of one anothe o coodinate thei use of the spectum. In noncoopeative coexistence, each netwok teats the othe net- 246 MHz 2465 MHz 247 MHz 2475 MHz 248 MHz MHz MHz MHz MHz 244 MHz 2425 MHz MHz MHz 245 MHz MHz MHz 2 7 IEEE 82. Ch 6 IEEE 82. Ch IEEE 82. Ch 242 MHz 244 MHz 246 MHz 248 MHz 24 MHz 242 MHz 244 MHz 246 MHz 248 MHz 242 MHz 2422 MHz 2424 MHz 2426 MHz 2428 MHz 243 MHz 2432 MHz 2434 MHz 2436 MHz 2438 MHz 244 MHz 2442 MHz 2444 MHz 2446 MHz 2448 MHz 245 MHz 2452 MHz 2454 MHz 2456 MHz 2458 MHz 246 MHz 2462 MHz 2464 MHz 2466 MHz 2468 MHz 247 MHz 2472 MHz 2474 MHz 2476 MHz 2478 MHz 248 MHz Abstact The apid gowth of the Intenet-of-Things (IoT) has led to a polifeation of low-powe wieless technologies. A majo challenge in designing an IoT netwok is to achieve coexistence between diffeent wieless technologies shaing the unlicensed 2.4 GHz ISM spectum. Although thee is significant liteatue on coexistence between IEEE and IEEE 82., the coexistence of Bluetooth Low Enegy (BLE) with othe technologies emains undestudied. In this wok, we examine coexistence between IEEE , BLE and IEEE 82., which ae widely used in esidential and industial wieless applications. We pefom a mathematical analysis of the effect of cosstechnology intefeence on the eliability of the affected wieless netwok in the physical (PHY) laye. We also set up and pefom PHY laye expeiments to veify the analytical esults. Finally, we extend the study to the Medium Access Contol (MAC) laye. Ou findings show that, even though the MAC laye mechanisms of IEEE and BLE impove eliability, coopeative solutions ae equied to achieve coexistence. Ch Fequency Cente / IMEC-NL, High Tech Campus 3, 5656 AE Eindhoven, The Nethelands of Electical Engineeing, Eindhoven Univesity of Technology, 56 MB Eindhoven, The Nethelands .nataajan@student.tue.nl, pouia.zand@imec-nl.nl, m.nabi@tue.nl Fequency Ch Depatment BLE Fig GHz ISM band: IEEE , BLE and IEEE 82. channels woks pesent as intefeence and pefoms intefeence mitigation. In coopeative coexistence, all the netwoks collaboate and coodinate thei use of the spectum in a fai way. An example use case of coopeative coexistence is a smat gateway that coodinates spectum usage between multiple netwoks that employ diffeent wieless technologies. In ode to popose a coexistence solution fo a given application, it is fist necessay to study the effect of cosstechnology intefeence on the pefomance of the involved wieless technologies. While existing studies in this topic aea povide an insight into the natue of the coexistence issue, they fail to systematically analyse the effect of coss-technology intefeence. As a esult, the outcomes ae quite inconclusive and sometimes even contadictoy. Futhemoe, no eseach on coexistence between IEEE , BLE and IEEE 82. has yet been undetaken, even though these technologies ae widely used in smat homes, smat buildings and industial wieless applications. To ty and fill this knowledge gap, we pefom a systematic analysis of coexistence between IEEE , BLE and IEEE 82.b. The choice of IEEE 82.b is abitay; this study can also be applied to othe vaiants of IEEE 82.. The contibutions of this wok can be summaised as follows: ) Adopting the coexistence methodology intoduced in [4] and applying it to IEEE , BLE and IEEE 82.b 2) Pefoming a mathematical analysis to study PHY laye coexistence of these technologies and veifying the analytical esults though expeiments 3) Studying MAC laye coexistence though expeiments 4) Poviding a basis to connect this study to eal-wold application equiements

2 II. R ELATED W ORK Thee is a significant amount of liteatue available on coexistence between IEEE and IEEE 82.. Likewise, the coexistence of Bluetooth Classic [5] with othe technologies has been studied extensively. Howeve, the coexistence of BLE with othe technologies emains undestudied. IEEE [6] specified ecommended pactices fo coexistence of IEEE 82.5 Wieless Pesonal Aea Netwoks (WPANs) with othe netwoks opeating in the same unlicensed fequency bands. The IEEE 82.9 Wieless Coexistence Woking Goup has extended this scope by developing standads fo coexistence between wieless technologies in the unlicensed fequency bands. Thei contibutions to the field included a coexistence methodology [4], which analytically estimates the effect of coss-technology intefeence on the eliability of netwoks. R. G. Gaoppo et al. [7] eseached the effect of IEEE 82. and Bluetooth Classic intefeence on IEEE and vice vesa though expeiments. They found that the Packet Eo Rate () of IEEE dops by aound 4% due to IEEE 82. intefeence and by less than % due to Bluetooth Classic intefeence. Moeove, IEEE is moe affected by the distance to the IEEE 82. intefee than Bluetooth Classic. They also obseved negligible effects on IEEE 82. o Bluetooth Classic, due to intefeence fom IEEE S. Silva et al. [8] studied the effect of IEEE 82., IEEE and Bluetooth Classic intefeence on BLE though expeiments. They obseved no effect on the and the Received Signal Stength Indicato (RSSI) of BLE as a esult of intefeence fom any of the othe technologies. This indicates that fequency hopping in BLE is vey effective in intefeence-avoidance. J. Wyffels et al. [9] eseached the intefeence effect of BLE advetising beacons on IEEE 82. though expeiments. They obseved that the impact of intefeence is significantly shaped by channel sepaation. At a channel sepaation of 7 MHz, they obseved pactically no impact on IEEE 82. taffic, wheeas at MHz, they obseved a dop of aound 5% in IEEE 82. thoughput. The existing coexistence studies in liteatue as discussed above, povide a limited analysis of the effect of intefeence. Futhemoe, the esults obtained ae athe inconclusive. To ty and bidge this gap, we set out to pefom a systematic study of coexistence though both mathematical analysis and expeiments. Futhemoe, we study coexistence between IEEE , BLE and IEEE 82., which is of inteest to esidential and industial wieless applications. (, D) D Affected Wieless Netwok The emainde of this pape is oganised as follows. Section II discusses some of the existing liteatue on coexistence. Section III descibes the mathematical analysis. Section IV discusses the outcomes of ou expeiments. Section V discusses the findings of ou study. Section VI pesents ou conclusions. Finally, Section VII discusses the pemises of this study as well as the scope fo futue wok. (, ) (d, ) Intefeing Wieless Netwok (e, ) d Fig. 2. Geometic model fom [4] III. M ATHEMATICAL A NALYSIS In ou mathematical analysis of coexistence, we adopt the methodology developed in [4] to estimate the caused by coss-technology intefeence, and apply it to IEEE , BLE and IEEE 82.b. This estimate can be used to estimate othe pefomance metics such as latency and thoughput. To make this pape self-contained and to ensue continuity, we include the deivation of the geneic methodology fom [4] hee, and discuss how we apply it to these technologies. In this analysis, we conside only the PHY layes of the involved wieless technologies. The effect of MAC laye mechanisms is consideed in the expeimental study discussed in Section IV. A. Methodology The methodology developed in [4] takes the geometic model of the Affected Wieless Netwok (AWN) and the Intefeing Wieless Netwok (IWN) as its stating point. Following this, a path-loss model is used to calculate the aveage Signalto-Intefeence Ratio (SIR) at the AWN eceive, eflecting the signal and intefeence tansmit powes and the geomety of the netwoks. A PHY laye model is then used to calculate the Symbol Eo Rate (SER) of the AWN as a function of the SIR at the AWN eceive, assuming continuous intefeence. Finally, a tempoal model takes into account the dynamic natue of the intefeence by modelling it as a pulse geneato with known statistical popeties, and calculates the AWN s as a function of SER. We analyse the following fou netwok configuations: ) AWN = IEEE , IWN = BLE 2) AWN = IEEE , IWN = IEEE 82.b 3) AWN = BLE, IWN = IEEE ) AWN = BLE, IWN = IEEE 82.b B. Geometic model The geometic model descibes the location of the nodes of the AWN and the IWN. We conside the simple configuation poposed in [4] shown in Fig. 2, whee each netwok consists of only two nodes. A moe complex geometic model could

3 Path-loss vs Distance Signal packet T Intefeence Enegy 4 Path-loss (db) 5 S S2 S3 S4... SLS 6 Time 7 Fig. 4. PHY laye model fom [4] and BLE have a eceive filte bandwidth of 2 MHz. PIf is theefoe calculated accodingly fo the fou netwok configuations. Finally, the SIR at the eceive, γ, is given by Eqn Distance (m) f γdb = PS,dB PI,dB γdb / γ = Fig. 3. Path-loss model fom [6] be used to study moe ealistic netwoks. It is futhe assumed that only one IWN node is nea the AWN, focusing only on the intefeence caused by that node on the AWN. In ode to study the wost case intefeence duing unidiectional tansfe, we assume the node at (, ) to be the eceive, the node at (, D) to be the tansmitte and the node at (d, ) to be the intefee. The same geometic model is used fo all fou netwok configuations. C. Path-loss model The distances in the geometic model ae tanslated into signal attenuation using the path-loss model. The path-loss model is chosen depending on the fequency band used and the envionment the netwoks opeate in. We use the path-loss model ecommended in [6] fo indoo envionments in the 2.4 GHz band. It is a piecewise linea model, descibed by Eqn. and shown in Fig. 3, that epesents fee-space path-loss up to 8 m, and a moe clutteed envionment beyond 8 m log (d).5m < d 8m pl(d) = () log (d/8) d > 8m Using the geomety of Fig. 2, the SIR, γ, at the eceive is calculated as follows. Fist, the signal and intefeence powes at the eceive, PS,dB and PI,dB, ae calculated using the well-known path-loss fomula, given the tansmitted signal and t t intefeence powes, PS,dB and PI,dB, and the coesponding distances, D and d. t PS,dB = PS,dB pl(d) t PI,dB = PI,dB pl(d) (2) Following this, the intefeence powe afte the eceive filte, PIf, is calculated depending on the elative bandwidths of the intefee, BI, and the eceive filte, BF, as discussed in [4]. PI BI BF f PI = (3) PI BF /BI BI > BF The occupied signal bandwidth of IEEE is 2 MHz, of BLE is MHz, and of IEEE 82.b is 22 MHz. IEEE (4) D. PHY laye model The PHY laye model is used to calculate the SER of the AWN as a function of the SIR at the eceive. We have adopted the basic PHY laye model fom [4] and modified it fo IEEE and BLE. The signal is a packet of LS symbols, each symbol of duation T, and the intefeence is continuous as shown in Fig. 4. All symbols ae assumed to be tansmitted though a common modulation scheme and code ate. The model could be extended to addess diffeent levels of obustness of the peamble and the data. The model stats with the SER expession fo the chosen modulation scheme in the pesence of Additive White Gaussian Noise (AWGN). Next, the elationship between ES /N and Signal-to-Noise Ratio (SNR) at the eceive, and theefoe SIR, is obtained. Finally, the ES /N tem in the SER expession is eplaced by the SIR. ) IEEE PHY model: The IEEE GHz PHY employs O-QPSK modulation and Diect Sequence Spead Spectum (DSSS) with bandwidth BS = 2 MHz, chip ate Rc = 2 kc/s, bit ate Rb = 25 kb/s and a codebook of M = 6 symbols []. Fo non-coheent demodulation, the SER, p, is given by Eqn. 5 []. M X M ES /N (/k ) p = /M ( )k e (5) k k=2 Assuming matched filteing at the eceive and half-sine wave pulse-shaping, we fist calculate Eb /N. Eb /N =.625 Rc /Rb SN R = 5 SN R (6) whee the DSSS pocess gain Rc /Rb = 8, SN R = PS /PNf, whee PS and PNf ae the signal and noise powes afte the eceive filte. Then, we convet fom Eb /N to ES /N. ES /N = log2 (M ) Eb /N = 2 SN R (7) Following this, we eplace the noise powe occuing afte the eceive filte with the equivalent intefeence powe. SN R = PS /PNf PS /PIf = γ ES /N = 2γ (8)

4 LI, pe LI sufficient duation to accommodate the signal packet. Depending on the andom position of the signal packet elative to the intefeence packet, thee possible scenaios emege, as shown in Fig. 5: no, patial, o full collision. Fo fixed LS and LI, the pobability mass function, fx (x), takes on the following geneic fom [4]. LS fx () = c fx (x) = c2 fx (K) = c3 fx (x) = Signal packet Fig. 5. Tempoal model fom [4] Substituting fo ES /N in Eqn. 5, the SER, p, as a function of SIR, γ, fo IEEE PHY is given by Eqn X k 6 p = /6 ( ) (9) e2γ(/k ) k k=2 2) BLE PHY model: The BLE PHY employs GFSK modulation with bandwidth BS = MHz, bit ate Rb = Mb/s, BT =.5 and modulation index h =.5 [2]. Fo noncoheent demodulation, the SER, p, is given by Eqn. []. () Following the steps used in the IEEE PHY model, we calculate ES /N as a function of SIR, γ. ES /N = Eb /N = BS /Rb SN R = SN R = γ () Substituting fo ES /N in Eqn., the SER, p, as a function of SIR, γ, fo BLE PHY is given by Eqn. 2. p = /2e γ/2 (2) E. Tempoal model The tempoal model convets fom SER to, taking the tempoal aspects of both the signal and the intefeence into account. We have adopted the tempoal model developed in [4]. The basic pinciple is to conside the pobability of collision between signal packets and intefeence packets. If X denotes the numbe of symbol collisions, then X is a andom vaiable with pobability mass function fx (x), whee x =,,..., LS, whee LS is the length of the signal packet. The is then given by Eqn. 3 [4]. P ER = LS X ( ( p)x )fx (x) (4) x = K +, K + 2,..., max(ls, LI ) whee c, c2 and c3 ae constants, and K is the maximum numbe of symbol collisions given by min(ls, LI ). Substituting fo fx (x) in Eqn. 3 and simplifying, the as a function of the SER, p, is given by Eqn. 5 [4]. Intefeence packet p = /2e ES /2N x =, 2,..., K (3) x= whee p is the SER. The pobability mass function, fx (x), depends on the length of the signal packet, LS, the length of the intefeence packet, LI, and the intefeence packet inteval, LI,pe. We conside the signal and intefeence packets to be of fixed lengths and the intefeence packet inteval to be fixed and of P ER = c2 (Kp + ( p)k )/p + c3 ( ( p)k ) (5) F. Results Using the methodology descibed above, we pefom a coexistence analysis between IEEE , BLE and IEEE 82.b fo the fou netwok configuations listed in the methodology section. Fo each of the fou netwok configuations, we study the effect of the following thee paametes on the : ) Intefee distance 2) Intefee packet inteval 3) Intefee channel sepaation In each of these thee scenaios, we vay the netwok paamete of inteest and fix the values of the emaining paametes. The fixed paametes in all thee scenaios ae as follows: a) AWN paametes: PSt = dbm, D = 8 m, T = 6µs (IEEE ), µs (BLE), LS = 28 bytes (IEEE ), 4 bytes (BLE) b) IWN paametes: PIt = dbm (IEEE and BLE), 2 dbm (IEEE 82.b), LI = 28 bytes (IEEE ), 4 bytes (BLE), 24 bytes (IEEE 82.b) The esults of the coexistence analysis ae shown in Fig. 6. ) Intefee distance: In this scenaio, the intefee distance fom the eceive d is vaied fom to m. The intefee packet inteval LI,pe is fixed at 2 ms fo IEEE and BLE, and ms fo IEEE 82.b. The tansmitte and intefee channels ae chosen as follows: IEEE on channel 2 (24 MHz), BLE on channel 3 (24 MHz) and IEEE 82.b on channel (242 MHz), thus constituting co-channel intefeence. All othe paametes ae fixed as specified ealie. The esults ae shown in Fig. 6a. As Fig. 6a demonstates, the BLE netwok is affected moe by IEEE intefeence than vice vesa. The IEEE netwok achieves % at a BLE intefee distance of aound 7 m, wheeas the BLE netwok equies an IEEE intefee distance of aound 7 m to achieve %. One eason fo this diffeence is the DSSS pocess gain (aound 9 db) in the IEEE netwok. Anothe eason is the longe channel-occupancy of IEEE

5 vs Intefee distance sig + BLE int (ana) sig + BLE int (exp) sig + 82.b int (ana) sig + 82.b int (exp) BLE sig int (ana) BLE sig int (exp) BLE sig + 82.b int (ana) BLE sig + 82.b int (exp) Intefee distance (m) (a) Intefee distance vs Intefee packet inteval sig + BLE int (ana) sig + BLE int (exp) sig + 82.b int (ana) sig + 82.b int (exp) BLE sig int (ana) BLE sig int (exp) BLE sig + 82.b int (ana) BLE sig + 82.b int (exp) Intefee packet inteval (ms) (b) Intefee packet inteval vs Intefee channel sepaation sig + BLE int (ana) sig + BLE int (exp) sig + 82.b int (ana) sig + 82.b int (exp) BLE sig int (ana) BLE sig int (exp) BLE sig + 82.b int (ana) BLE sig + 82.b int (exp) Intefee channel sepaation (MHz) (c) Intefee channel sepaation Fig. 6. Results of PHY laye coexistence analysis and expeiments packets (aound 4 ms) compaed to BLE packets (aound.32 ms), thus causing the IEEE intefee to affect the BLE netwok moe. It is also woth noting that, up to distances aound 2 m, IEEE 82.b intefeence affects the IEEE netwok moe than the BLE netwok. This is due to the shote on- ai time of BLE packets compaed to IEEE packets. This inceases the likelihood that the BLE signal can avoid collision with the IEEE 82.b intefee. 2) Intefee packet inteval: In this scenaio, the intefee packet inteval LI,pe is vaied fom 5 ms to s. The intefee distance d is fixed at 5 m and and the tansmitte and intefee channels ae chosen as follows: IEEE on channel 2 (24 MHz), BLE on channel 3 (24 MHz) and IEEE 82.b on channel (242 MHz), thus constituting co-channel intefeence. All othe paametes ae fixed as specified ealie. The esults ae shown in Fig. 6b. As Fig. 6b demonstates, the BLE netwok is affected maginally moe by the IEEE netwok than vice vesa. The IEEE netwok achieves % at a BLE intefee packet inteval of aound 35 ms, wheeas the BLE netwok achieves % at an IEEE intefee packet inteval of aound 45 ms. The easons fo this diffeence ae the DSSS pocess gain and the longe channeloccupancy of the IEEE netwok, as discussed ealie. Anothe obsevation is that the BLE netwok is affected much less (aound 5 times) by IEEE 82.b intefeence than by IEEE intefeence, inspite of the highe tansmit powe of the IEEE 82.b intefee (2 dbm) compaed to IEEE ( dbm). Thee ae two easons fo this. Fist, the IEEE intefee has a highe channel-occupancy compaed to the IEEE 82.b intefee. Second, the IEEE 82.b intefeence powe scales down as the wideband IEEE 82.b intefeence passes though the naowband BLE eceive filte. 3) Intefee channel sepaation: In this scenaio, the intefee channel sepaation fom the tansmitte is vaied fom -5 to 5 MHz, thus constituting adjacent channel intefeence. The intefee distance d is fixed at 5 m. The intefee packet inteval LI,pe is fixed at 2 ms fo IEEE and BLE, and ms fo IEEE 82.b. All othe paametes ae fixed as specified ealie. The esults ae shown in Fig. 6c. As Fig. 6c demonstates, the BLE netwok is once again affected moe by the IEEE netwok than vice vesa. At an intefee channel sepaation of MHz, the BLE netwok has a of aound 22%, wheeas the of the IEEE netwok dops to aound %. At a 2 MHz channel sepaation, the dops to almost zeo in both configuations. In case of IEEE 82.b intefeence, both IEEE and BLE netwoks get affected seveely up to aound MHz channel sepaation, afte which the dops down to almost zeo. IV. E XIMENTAL S TUDY To veify the esults of the mathematical analysis, we pefom expeiments by setting up two netwoks, the AWN and the IWN. Each netwok consists of two wieless nodes, one tansmitte (AWN Tx o IWN Tx) and one eceive (AWN Rx o IWN Rx). The expeimental setup of the configuations with IEEE o BLE intefeence is shown in Fig. 7a and with IEEE 82.b intefeence is shown in Fig. 7b. Fo the wieless nodes of the IEEE o BLE netwok,

6 AWN Tx IWN Rx CC265 SensoTag + Tx Test FW CC265 SensoTag + Int Test FW the IWN Rx. The is calculated based on the numbe of packets eceived coectly at the AWN Rx. B. Expeimental Setup fo MAC Laye Coexistence Study AWN Rx IWN Tx CC265 SensoTag + Rx Test FW CC265 SensoTag + Int Test FW (a) IEEE and BLE intefeence AWN Tx IWN Rx CC265 SensoTag + Tx Test FW Laptop + NetScanTools AWN Rx Laptop + NetScanTools IWN Tx CC265 SensoTag + Rx Test FW (b) IEEE 82.b intefeence Fig. 7. Setup fo PHY and MAC laye coexistence expeiments we use the Texas Instuments SensoTag [] based on the CC265 multi-standad 2.4 GHz wieless mico-contolle [2] that can opeate in eithe IEEE o BLE mode. Fo IEEE 82.b intefeence, we set up an adhoc wieless netwok between two laptops and use the NetScanTools Po Packet Floode tool [3] to geneate IEEE 82.b taffic with specified paametes. We study the coexistence of IEEE and BLE with espect to the PHY laye paametes such as modulation scheme, data ate, bandwidth, packet size and packet inteval. We futhe extend the expeiments to the MAC laye to study the impovement in coexistence caused by mechanisms such as Caie Sense Multiple Access (CSMA) and packet etansmissions in IEEE , and Adaptive Fequency Hopping (AFH) and packet etansmissions in BLE. A. Expeimental Setup fo PHY Laye Coexistence Study Fo the PHY laye coexistence expeiments, we develop custom fimwae on the Texas Instuments SensoTag using the PHY laye Application Pogamming Intefaces (APIs) fo the CC265 platfom povided by Contiki OS [4]. Ou custom fimwae allows configuation of the PHY laye paametes of the IEEE and BLE AWN and IWN such as tansmit powe, channel, packet length and packet inteval. As mentioned ealie, IEEE 82.b intefeence is geneated using an adhoc netwok of two laptops unning the NetScanTools Po Packet Floode tool. In each test case, we tansmit packets at andom time intevals fom the AWN Tx to the AWN Rx and we tansmit peiodic intefeence packets fom the IWN Tx to Fo the MAC laye coexistence expeiments, we develop custom applications that un on top of the potocol stacks of IEEE (TIMAC [5]) and BLE (BLE-stack [6]) povided by Texas Instuments. The applications allow configuation of the MAC laye paametes such as selecting beacon/non-beacon mode and enabling/disabling packet etansmission in IEEE , and configuing connection inteval and channel map in BLE. In the IEEE MAC, we select non-beacon mode, and enable acknowledgement with packet etansmission. In the BLE MAC, we set the connection inteval to the desied packet inteval, and configue the channel map with two channels, one ovelapping with the selected IEEE o IEEE 82.b channel, and the othe at least 2 MHz away. The IEEE 82.b intefeence is geneated as mentioned in the PHY laye coexistence study. The is calculated based on the numbe of etansmissions at the AWN Tx. C. Results We pefom PHY laye coexistence expeiments fo all fou netwok configuations and fo all thee paamete scenaios as mentioned in Section III. The PHY laye expeimental esults ae shown in Fig. 6 alongside the PHY laye analytical esults. As Fig. 6 demonstates, the expeimental esults match the analytical esults with a Nomalised Mean Squae Eo (NMSE) of aound.78% fo IEEE and BLE intefeence. In the case of IEEE 82.b intefeence, the NMSE is highe at aound %. Given the pactical limitation on sepaating the coexisting netwoks in distance, paticulaly in indoo envionments, we conside only packet inteval and channel sepaation as paametes fo the MAC laye coexistence expeiments. The MAC laye expeimental esults ae shown in Fig. 8 alongside the PHY laye analytical esults. As Fig. 8 demonstates, the MAC laye mechanisms mentioned ealie lead to an impovement in coexistence pefomance. In all fou netwok configuations, enabling packet etansmission impoves eliability at the cost of inceased latency. In ode to etain eliability as the pefomance metic, we have calculated the based on the numbe of etansmissions. The effect of CSMA in IEEE is evident in case of IEEE 82.b intefeence, whee the eliability of IEEE impoves fom the coesponding PHY laye scenaio, e.g., dops fom aound 48% to aound 33% at ms intefeence packet inteval. In the case of BLE intefeence, the BLE netwok hops between two channel. This esults in educed intefeence with the IEEE netwok, making it difficult to obseve the effect of CSMA sepaately. It is woth noting that BLE lacks a CSMA featue. As expected, AFH in BLE esults in impoved eliability compaed to the single-channel scenaio consideed in the

7 vs Intefee packet inteval sig + BLE int (PHY, ana) sig + BLE int (MAC, exp) sig + 82.b int (PHY, ana) sig + 82.b int (MAC, exp) BLE sig int (PHY, ana) BLE sig int (MAC, exp) BLE sig + 82.b int (PHY, ana) BLE sig + 82.b int (MAC, exp) Intefee packet inteval (ms) (a) Intefee packet inteval vs Intefee channel sepaation sig + BLE int (PHY, ana) sig + BLE int (MAC, exp) sig + 82.b int (PHY, ana) sig + 82.b int (MAC, exp) BLE sig int (PHY, ana) BLE sig int (MAC, exp) BLE sig + 82.b int (PHY, ana) BLE sig + 82.b int (MAC, exp) ) At shot intefeence packet intevals, e.g., ms, the eliability of the AWN (IEEE o BLE) is aound 6%, when consideing the PHY laye only. The MAC laye mechanisms such as AFH in BLE, and CSMA as well as packet etansmission in IEEE , impove the eliability to aound 85%. 2) In ode to study applications with lowe data ates, we incease the intefeence packet inteval to 2 ms, then 5 ms, then all the way to one second. The eliability of the AWN inceases steadily as a esult, e.g., 8% at 2 ms, 93% at 5 ms and 99% at one second. 3) In a eal deployment of a dense netwok, with to nodes installed in the same tansmission ange, i.e., 3 to 5 m, the data ate of a single node could be much moe than ms, e.g., second. Howeve, the entie IWN can be consideed as a single intefeing node with a highe data ate ( to times moe than a single node), theeby deceasing the eliability of the AWN. 4) In the case of IEEE 82. intefeence, the eliability of the AWN is aound 95%, 5% and 5% at an IEEE 82. taffic load of %, % and 2% espectively. This is a significant decease in eliability and necessitates a coexistence solution..4.3 VI. C ONCLUSION Intefee channel sepaation (MHz) (b) Intefee channel sepaation Fig. 8. Results of MAC laye coexistence expeiments PHY laye expeiments. In the MAC laye expeiments, the BLE netwok hops between two channels in both BLE as AWN and IWN scenaios. This esults in educed intefeence with the IEEE netwok, indiectly impoving the eliability by a facto of two. Fo instance, the of BLE as AWN dops fom aound 44% to aound 22% at a ms intefeence packet inteval. This esult can be extapolated to a BLE channel map with a geneic numbe of channels, povided adequate channel sepaation between the coexisting netwoks is guaanteed. V. D ISCUSSION Both IEEE and BLE ae designed fo a vaiety of applications, such as safety and potection, industial automation and pocess monitoing, with widely diffeent data ate and latency equiements. This is evident fom the suppoted BLE connection inteval ange (7.5 ms to 4 seconds) and the IEEE beacon inteval ange (5.36 ms to seconds). In this pape, we model the data ate using packet inteval in both the PHY and MAC layes. Based on this, we study netwok eliability ove a wide ange of packet intevals ( ms to one second). Ou main findings ae listed below: This pape has descibed a systematic study of coexistence between IEEE , BLE and IEEE 82.b in the unlicensed 2.4 GHz ISM band. Fist, we pefomed a mathematical analysis and quantified the effect of vaying the spatial, tempoal and fequency paametes of the intefeence on the eliability of the netwok. We compaed the esilience of the PHY layes of the afoementioned technologies against coss-technology intefeence. Then, we set up expeiments with eal wieless netwoks and veified ou analytical esults. Finally, we extended the expeiments to the MAC laye to study the effect of MAC laye mechanisms on coexistence pefomance. In geneal, we found that BLE is affected moe by IEEE intefeence than vice vesa. This could be attibuted to the DSSS pocess gain and longe channel-occupancy of IEEE compaed to BLE. On the othe hand, we found that BLE is moe esilient than IEEE against IEEE 82. intefeence. This is mainly due to BLE s shote channel-occupancy than IEEE , which exposes it less to IEEE 82. intefeence. In ode to connect this study to eal-wold applications, we have povided a basis to map diffeent applications, based on thei QoS equiements, to diffeent egions of the eliability vs. intefee packet inteval cuve. Such a mapping helps to identify egions of inteest that equie a coexistence solution. Futhemoe, the study of eliability vs. intefee channel sepaation could be useful in developing a fequency-domain coopeative coexistence solution.

8 VII. S COPE FOR F UTURE W ORK In this pape, we have consideed a simple geometic configuation with each netwok consisting of two nodes. This could be extended to a moe complex configuation to study moe ealistic netwoks. In the PHY laye model, we have assumed the packet to be homogeneous in obustness. While this consevative model pefoms accuately at low SIR, it could be extended to addess the diffeent levels of obustness of the data and the peamble potion of the packets. R EFERENCES [] IEEE Standad fo Local and metopolitan aea netwoks - Pat 5.4: Low-Rate Wieless Pesonal Aea Netwoks (LR-WPANs), IEEE Std , 2. [2] Bluetooth Specification Vesion 4.2, Coe Vesion 4.2, 24. [3] IEEE Standad fo Infomation technology - Telecommunications and infomation exchange between systems - Local and metopolitan aea netwoks - Specific equiements Pat : Wieless LAN Medium Access Contol (MAC) and Physical Laye (PHY) Specifications, IEEE Std , 22. [4] S. J. Shellhamme, Estimation of Packet Eo Rate Caused by Intefeence using Analytic Techniques - A Coexistence Assuance Methodology, IEEE P82.9 Wieless Coexistence, 25. [5] Bluetooth Specification Vesion 2. + EDR, Coe Vesion 2. + EDR, 27. Poweed by TCPDF ( [6] IEEE Recommended Pactice fo Infomation technology - Local and metopolitan aea netwoks - Specific equiements - Pat 5.2: Coexistence of Wieless Pesonal Aea Netwoks with Othe Wieless Devices Opeating in Unlicensed Fequency Bands, IEEE Std , 23. [7] R. G. Gaoppo, L. Gazzaini, S. Giodano, and L. Tavanti, Expeimental assessment of the coexistence of WiFi, ZigBee, and Bluetooth devices, IEEE Intenational Symposium on a Wold of Wieless, Mobile and Multimedia Netwoks (WoWMoM), pp. 9, 2. [8] S. Silva, T. Fenandes, A. Valente, and A. Moeia, Coexistence and Intefeence Tests on a Bluetooth Low Enegy Font-End, IEEE Science and Infomation Confeence (SAI), pp. 4 8, 24. [9] J. Wyffels, J.-P. Goemaee, B. Nauwelaes, and L. de Stycke, Influence of Bluetooth Low Enegy on WiFi Communications and Vice Vesa, Euopean Confeence on the Use of Moden Infomation and Communication Technologies, vol. 32, pp , 24. [] Coexistence analysis of IEEE Std with othe IEEE standads and poposed standads, IEEE P82.5 Wieless Pesonal Aea Netwoks, 2. [] SimpleLink Multi-standad SensoTag. [Online]. Available: [2] CC265 SimpleLink multi-standad 2.4 GHz ulta-low powe wieless MCU. [Online]. Available: [3] NetScanTools intenet and netwok infomation toolkits fo Windows. [Online]. Available: [4] Contiki: The Open Souce OS fo the Intenet of Things. [Online]. Available: [5] IEEE Medium Access contol (MAC) softwae stack. [Online]. Available: [6] Bluetooth low enegy softwae stack. [Online]. Available: