Tsarin Sarrafa Mai Rukuni na LED-Hudu da LED-Biyu don Sadarwar Haske da ake iya Gani: Nazari da Tsari

1. Gabatarwa & Bayyani

Sadarwar Haske da ake iya Gani (VLC) wata fasaha ce mai tasowa da ta dace da sadarwar RF, tana amfani da LED don haskakawa da watsa bayanai. Wata babbar kalubale a cikin VLC ita ce samar da sigina masu kyau, masu ƙima na gaske waɗanda suka dace da daidaita ƙarfin LED, galibi suna buƙatar daidaiton Hermitian a cikin tsarin OFDM wanda ke raba ingancin yanki. Wannan takarda tana ba da sabbin dabarun sarrafa rukuni na yanki na sarari waɗanda ke ƙetare wannan ƙuntatawa.

2. Tsare-tsaren Sarrafa da aka Tsara

Babban gudummawar ita ce tsare-tsaren sarrafa guda uku waɗanda ke amfani da LED da yawa don watsa alamomin rukuni ba tare da daidaiton Hermitian ba.

2.1 Sarrafa Rukuni na LED-Hudu (QCM)

Yana amfani da LED huɗu. Girman sassan gaske da na hasashe na alamar rukuni (misali, QAM) ana isar da su ta hanyar ƙarfin LED biyu. Bayanin alamar (tabbatacce/mara kyau) ana isar da shi ta hanyar tsara sarari—zaɓin wane takamaiman biyu na LED aka kunna. Wannan yana raba girman da alama zuwa nau'ikan zahiri daban-daban (ƙarfi da sarari).

2.2 Sarrafa Rukuni na LED-Biyu (DCM)

Wani tsari mai inganci wanda ke amfani da LED biyu kawai. Yana amfani da wakilcin polar na alamar rukuni $s = re^{j\theta}$.

LED ɗaya yana watsa girman $r$ ta hanyar daidaita ƙarfi.
Dayan LED yana watsa lokacin $\theta$ ta hanyar daidaita ƙarfi (bayan daidaitawa da ya dace zuwa ƙima mai kyau).

Wannan kai tsaye yana sanya sigogin halitta na alamar rukuni zuwa tashoshi na zahiri daban-daban.

2.3 Sarrafa Sarari DCM (SM-DCM)

Wani haɓaka wanda ya haɗa DCM tare da ƙa'idodin Sarrafa Sarari (SM). Tsarin yana amfani da tubalan DCM guda biyu (kowanne yana da LED biyu). Ƙarin bit na fihirisa yana zaɓar wane tubalin DCM ke aiki a cikin amfani da tashoshi da aka bayar. Wannan yana ƙara girman sarari don ƙarin watsa bayanai, yana inganta ingancin yanki.

3. Cikakkun Bayanai na Fasaha & Tsarin Tsarin

3.1 Tsarin Lissafi

Yi la'akari da alamar sarrafa rukuni $s = s_I + j s_Q$. Bari $\mathbf{x} = [x_1, x_2, ..., x_N]^T$ ya zama vector na ƙarfi don $N$ LED.

Don QCM ($N=4$): Tsarin yana tabbatar da $x_i \ge 0$. Alamar $s_I$ da $s_Q$ suna ƙayyade takamaiman tsarin sarari (zaɓin biyu na LED). Misali: $\text{Idan } s_I \ge 0, s_Q \ge 0: \mathbf{x} = [|s_I|, |s_Q|, 0, 0]^T$ $\text{Idan } s_I < 0, s_Q \ge 0: \mathbf{x} = [0, |s_Q|, |s_I|, 0]^T$ da sauransu.

Don DCM ($N=2$): Bari $s = re^{j\theta}$, tare da $r \ge 0$, $\theta \in [0, 2\pi)$. Wani yiwuwar tsari shine: $x_1 = r$ (LED mai girman) $x_2 = \frac{\theta}{2\pi} \cdot P_{avg}$ (LED na lokaci, wanda aka auna ta matsakaicin ƙarfi)

3.2 Zanen Na'urar Gano

Takardar ta gabatar da na'urori masu gano guda biyu don tsare-tsaren da aka tsara a cikin tsarin OFDM (QCM-OFDM, DCM-OFDM):

Na'urar Gano Zero-Forcing (ZF): Na'urar gano layi wacce ke jujjuya matrix tashoshi. Mai sauƙi amma yana iya ƙara ƙarar amo. Vector alamar da aka ƙiyasta $\hat{\mathbf{s}}_{ZF} = (\mathbf{H}^H\mathbf{H})^{-1}\mathbf{H}^H \mathbf{y}$, inda $\mathbf{H}$ shine matrix tashoshi MIMO kuma $\mathbf{y}$ shine vector sigina da aka karɓa.
Na'urar Gano Mafi ƙarancin Nisa (MD): Na'urar gano mara layi, mafi kyau (a ma'anar ML don AWGN) wacce ke gano alamar da aka watsa wacce ke rage nisan Euclidean zuwa sigina da aka karɓa: $\hat{\mathbf{s}}_{MD} = \arg\min_{\mathbf{s} \in \mathcal{S}} ||\mathbf{y} - \mathbf{H}\mathbf{x}(\mathbf{s})||^2$, inda $\mathcal{S}$ shine saitin duk yiwuwar alamomin rukuni kuma $\mathbf{x}(\mathbf{s})$ shine tsarin sarrafa.

4. Sakamakon Gwaji & Aiki

Takardar tana kimanta aiki ta hanyar nazarin Kuskuren Bit (BER) da kuma siminti.

BER vs. SNR: Hotuna sun nuna cewa DCM da SM-DCM sun fi QCM aiki don ingancin yanki da aka bayar. SM-DCM yana ba da mafi kyawun aiki saboda ƙarin bambancin sarari da ribar lambobi daga bit na fihirisa.
Kewayon Ƙimar da za a iya Samu: Ta amfani da ƙaƙƙarfan iyakoki na sama na BER na nazari da kuma rarraba sarari na SNR da aka karɓa, marubutan sun lissafta kuma suka zana kewayon ƙimar da za a iya samu don manufar BER (misali, $10^{-3}$). Waɗannan kewayon suna nuna yankuna a sarari inda sadarwa mai aminci zai yiwu don QCM, DCM, da SM-DCM, suna nuna fifikon ɗaukar hoto da ƙimar SM-DCM.
Babban Bincike: Tsare-tsaren da aka tsara, musamman DCM da SM-DCM, suna cimma kwatankwacin ko mafi kyawun aikin kuskure fiye da na al'ada na OFDM na tushen daidaiton Hermitian (kamar DCO-OFDM) yayin da suke ba da cikakken watsa alamar rukuni a kowane amfani da tashoshi, yana inganta ingancin yanki sau biyu a cikin yankin rukuni.

5. Tsarin Nazari & Misalin Lamari

Tsarin don Kimanta Tsare-tsaren Sarrafa VLC:

Ingancin Yanki (bits/s/Hz): Yi lissafi bisa girman tauraro da bit na sarari (misali, SM-DCM: $\log_2(M) + 1$ bit a kowane amfani da tashoshi, inda $M$ shine girman QAM, kuma +1 shine bit na fihirisa na sarari).
Ingancin Wutar Lantarki & Kewayon Aiki: Yi nazarin layin LED da ake buƙata da kewayon aiki don daidaita ƙarfi na sassan girman da lokaci.
Rikitarwar Mai Karɓa: Kwatanta farashin lissafi na gano ZF da MD, musamman don manyan tsarin MIMO.
Ƙarfin Juriya ga Yanayin Tashoshi:
Yi siminti na aiki a ƙarƙashin nau'ikan tashoshi na VLC na cikin gida daban-daban (misali, nunin Lambertian, kasancewar cikas).

Misalin Lamari - Wurin Hotspot na Li-Fi na Cikin Gida: Yi la'akari da ɗaki mai LED ɗin rufi 4 (an shirya su a cikin murabba'i). Yin amfani da SM-DCM tare da 16-QAM ($\log_2(16)=4$ bit) da bit ɗaya na fihirisa na sarari (zaɓi tsakanin tubalan DCM guda biyu na LED biyu kowanne), tsarin yana watsa bit 5/amfani da tashoshi. Idan tazarar subcarrier OFDM ita ce 100 kHz, ƙimar bayanai ɗanyan kowane subcarrier shine 500 kbps. Tare da subcarriers 512, jimlar ƙimar bayanai ta kai ~256 Mbps, wanda ya dace da babban gudun intanet na cikin gida mara waya, ba tare da buƙatar kayan aiki na daidaiton Hermitian ba.

6. Aikace-aikace na Gaba & Hanyoyin Bincike

Tsarin RF/VLC na Haɗin gwiwa: Yin amfani da DCM/SM-DCM don saukarwa (babban gudun VLC) da RF don hawa sama, inganta ka'idojin mika wuya.

Fuskar Tunani Mai Hikima (IRS) don VLC: Haɗa saman ƙasa don sarrafa hanyoyin haske da sauri, haɓaka aikin SM-DCM a cikin yanayin rashin gani. Bincike daga Lab na Media na MIT kan saman shirye-shirye na iya zama dacewa.

Gano Tushen Koyon Injin: Maye gurbin na'urori masu gano ZF/MD na al'ada tare da cibiyoyin jijiyoyi masu zurfi (DNNs) don haɗin ƙiyasin tashoshi da gano alama a cikin yanayin VLC mai ƙarfi, kama da ayyuka a cikin RF kamar "DeepMIMO".

Daidaituwa: Turawa don haɗa tsare-tsaren sarrafa yanki na sarari kamar DCM a cikin IEEE 802.11bb (Li-Fi) na gaba ko wasu ƙa'idodin VLC.

VLC mai Tattara Makamashi: Haɗin gwiwar tsara alamun DCM don inganta ƙimar bayanai da isar da wutar lantarki DC a lokaci guda don na'urorin IoT, wani batu da aka bincika a cikin ayyuka kamar "Simultaneous Lightwave Information and Power Transfer (SLIPT)".

7. Nassoshi

Narasimhan, T. L., Tejaswi, R., & Chockalingam, A. (2016). Quad-LED and Dual-LED Complex Modulation for Visible Light Communication. arXiv preprint arXiv:1510.08805v3.

Kahn, J. M., & Barry, J. R. (1997). Wireless infrared communications. Proceedings of the IEEE.

Mesleh, R., et al. (2008). Spatial Modulation. IEEE Transactions on Vehicular Technology.

IEEE Standard for Local and metropolitan area networks--Part 15.7: Short-Range Wireless Optical Communication Using Visible Light. IEEE Std 802.15.7-2018.

O'Brien, D. C., et al. (2008). Visible light communications: Challenges and possibilities. IEEE PIMRC.

Zhu, X., & Kahn, J. M. (2002). Free-space optical communication through atmospheric turbulence channels. IEEE Transactions on Communications.

8. Nazari na Asali & Fahimtar Kwararru

Fahimta ta Asali: Wannan takarda ba wani ƙarin gyara ne kawai na sarrafa VLC ba; shine sake tunani na asali na matsalar "rukuni-zuwa-gaske" na canjin sigina wanda ya addabi VLC-OFDM. Ta hanyar cire bayanin alama/lokaci daga yankin ƙarfi zuwa yankin sarari, marubutan sun raba ƙuntatawa na lissafi (daidaiton Hermitian) daga na zahiri (rashin kyau na LED). Wannan yana tunawa da canjin tsarin da CycleGAN (Zhu et al., 2017) ya gabatar a cikin hangen nesa na kwamfuta, wanda ya raba fassarar salo da abun ciki ta amfani da daidaiton zagaye maimakon bayanan biyu. A nan, rabuwa yana tsakanin wakilcin algebra na sigina da hanyar fitar da shi ta zahiri.

Kwararar Hankali & Gudummawa: Ci gaba daga QCM (LED 4, mai fahimta amma mai girma) zuwa DCM (LED 2, kyakkyawan taswira na polar) zuwa SM-DCM (ƙara fihirisar sarari mai ɗauke da bayanai) yana da kyau a hankali. Yana bin tafarkin aikin injiniya na al'ada: fara da mafita mai ƙarfi, nemo mafi kyawun wakilcin lissafi, sannan a sanya ƙarin digiri na 'yanci don inganci. Babban gudummawar fasaha ita ce tabbatar da cewa wakilcin polar ($r$, $\theta$) yana siffanta mafi dacewa da inganci ga Layer na zahiri na LED-biyu fiye da Cartesian ($I$, $Q$). Wannan ya yi daidai da binciken da aka samu a cikin RF massive MIMO inda wakilcin sararin katako (kwanƙwasa) sau da yawa yana sauƙaƙa sarrafawa.

Ƙarfi & Kurakurai: Babban ƙarfi shine ribar ingancin yanki—yana inganta shi sau biyu idan aka kwatanta da OFDM na daidaiton Hermitian. Iyakoki na BER da kewayon ƙimar suna ba da ingantaccen shaida, mai ƙima. Duk da haka, nazarin yana da makafai. Na farko, yana ɗauka cikakken bayanin yanayin tashoshi (CSI) da LED masu daidaitawa, wanda ba shi da mahimmanci a cikin tashoshi na VLC masu yaduwa tare da hanyoyi da yawa. Na biyu, kewayon aiki da ake buƙata don "lokacin" LED a cikin DCM an lulluɓe shi. Sanya lokaci mai ci gaba $\theta \in [0, 2\pi)$ a layi daya zuwa ƙarfi na iya buƙatar LED masu kyakkyawan layi a kan duk kewayon aikin su, wani sanannen batu a cikin VLC na analog. Na uku, ma'aunin kwatankwacin ya ɗan kunkuntar ne. Mafi ingantaccen ma'auni zai kasance a kan index modulation OFDM (IM-OFDM) na zamani ko asymmetrically clipped optical OFDM (ACO-OFDM) a ƙarƙashin ƙuntatawa na jimlar wutar lantarki da bandwidth iri ɗaya.

Fahimta mai Aiki: Ga masu bincike da injiniyoyi: 1. Mayar da hankali kan DCM, ba QCM ba. DCM shine wuri mai daɗi. Bukatar LED 2 tana sa ya zama mai amfani nan da nan ga yawancin fitilun Li-Fi waɗanda galibi suna da guntuwar LED da yawa. Masana'antu yakamata su yi samfuri na masu karɓa na DCM. 2. Haɗin gwiwa tare da ƙiyasin tashoshi. Mataki na gaba mai mahimmanci shine haɓaka ingantattun algorithms na ƙiyasin tashoshi, masu ƙarancin kaya waɗanda aka keɓance don tsarin sigina na DCM, watakila ta amfani da alamomin matukin jirgi da aka saka a cikin rafukan girman/lokaci da kansu. 3. Bincika taswirar marasa layi. Maimakon taswirar lokaci-zuwa-ƙarfi na layi, bincika dabarun haɗawa marasa layi (wanda aka yi wahayi ta hanyar haɗawa na $\mu$-law a cikin sauti) don rage matsalar kewayon aiki na LED da inganta ingancin wutar lantarki. 4. Haɗa tare da sabbin kayan aiki. Haɗin gwiwa tare da masana'antun LED don tsara jerin micro-LED inda kowane pixel zai iya zama daidaitacce don DCM/SM-DCM, ƙirƙirar haɗin kai na sadarwa da nuni—wani ra'ayi da bincike kan Tsarin Sadarwar Haske da Nuni (LiCaD) ya nuna. A ƙarshe, wannan aikin yana ba da hanyar fita mai inganci ta ka'ida da kuma mai ban sha'awa ta zahiri daga takalmin daidaiton Hermitian. Tasirinsa na zahiri zai dogara da magance ƙalubalen aiwatarwa kai tsaye, matsawa daga ka'idar kyakkyawa zuwa ingantattun tsarin daidaitattu.

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