simulation: Enable RX1 and RX2

1 files changed, 67 insertions, 42 deletions

diff --git a/simulation.scm b/simulation.scm
index 314c15d..061c703 100644
--- a/simulation.scm
+++ b/simulation.scm
@@ -12,9 +12,9 @@
   #:use-module (fibers timers))
 
 (define RX1 1) ; s (has to be between 1-15s)
-(define RX2 (1+ RX1)) ; s
-(define RECEIVE_DELAY1 1) ; s
-(define RECEIVE_DELAY2 (1+ RECEIVE_DELAY1)) ; s
+(define RX2 (+ 2 RX1)) ; s
+(define RECEIVE_DELAY1 3) ; s
+(define RECEIVE_DELAY2 (+ 2 RECEIVE_DELAY1)) ; s
 (define RETRANSMISSION_DELAY 2) ; s
 ;; From RP002 (Regional Parameters):
 ;; MAC commands exist in the LoRaWAN® specification to change the value of
@@ -62,6 +62,11 @@
   (put-message *id-channel-in* #t)
   (get-message *id-channel-out*))
 
+
+;; For timer operations
+(define (seconds->time-unit s)
+  (* internal-time-units-per-second s))
+
 ;; For End-Device <--> Radio <--> Gateway
 ;; type can be:
 ;; '[up/down]link-start
@@ -113,8 +118,6 @@
   (define internal-com (make-channel))
   ;; Make all atomic
   (define channel initial-channel)
-  (define (listening-to? chn)
-    (= channel chn))
 
   ;; TODO: Unhardcode me
   (define time-on-air 0.01)
@@ -147,7 +150,56 @@
       (sleep time-on-air)
       (put-message upstream-chn (make-radio-event 'uplink-end event-id channel frame))))
 
+
+  (define (receive-window channel time)
+    (define (listening-to? chn)
+      (= channel chn))
+
+    (define (detect-preamble)
+      (let wait-for-downlink-start ()
+        (let ((msg (perform-operation
+                     (choice-operation
+                       (wrap-operation (sleep-operation time)
+                                       (lambda _ 'time-is-out))
+                       (get-operation downstream-chn)))))
+          (match msg
+            ;; We got the preamble in time
+            (($ <radio-event> 'downlink-start message-id (= listening-to? chn) frame)
+             (ll "Device ~a got preamble" id)
+             message-id)
+            ;; No preamble in time
+            ('time-is-out #f)
+            ;; Current message is not a preamble, continue
+            (_ (wait-for-downlink-start))))))
+
+    (define (demodulate message-id)
+      (let wait-for-downlink-end ((interference? #f))
+        (let ((part-of-same-message? (lambda (i) (= message-id i)))
+              (msg (get-message downstream-chn)))
+          (match msg
+            (($ <radio-event> 'interference
+                (= part-of-same-message? id)
+                (= listening-to? chn)
+                frame)
+             (wait-for-downlink-end #t)) ;; Got interference
+            (($ <radio-event> 'downlink-end
+                (= part-of-same-message? id)
+                (= listening-to? chn)
+                frame)
+             (and (not interference?) frame))
+            (_ (wait-for-downlink-end interference?))))))
+
+    (put-message internal-com 'wait)
+    (let* ((preamble-id (detect-preamble))
+           (result      (and preamble-id (demodulate preamble-id))))
+      (put-message internal-com 'continue)
+      result))
+
   (define (device-operation)
+    (define (wait-until t)
+      (perform-operation
+        (timer-operation t)))
+
     (define current-frame 0)
     (forever
       ;; TODO check to-confirm
@@ -156,43 +208,16 @@
 
       (send-uplink-frame current-frame id #t)
       (set! current-frame (1+ current-frame)) ;; TODO: improve
-      (sleep RECEIVE_DELAY1) ;; TODO: make sure this is ok
-      (put-message internal-com 'wait)
-      (let ((until (+ (get-internal-real-time)
-                      (* RX1 internal-time-units-per-second))))
-        ;; TODO: listen to the first, and then hook to its radio-event-id
-        (let wait-for-downlink-start ()
-          (let ((msg (perform-operation
-                       (choice-operation
-                         (wrap-operation (timer-operation until)
-                                         (lambda _ 'time-is-out))
-                         (get-operation downstream-chn)))))
-            (ll "~a" msg)
-            (match msg
-              ;; We got the preamble in time
-              (($ <radio-event> 'downlink-start message-id (= listening-to? chn) frame)
-               (ll "Device ~a got preamble" id)
-               (let wait-for-downlink-end ((interference? #f))
-                 (let ((part-of-same-message? (lambda (i) (= message-id i)))
-                       (msg (get-message downstream-chn)))
-                   (match msg
-                     (($ <radio-event> 'interference
-                         (= part-of-same-message? id)
-                         (= listening-to? chn)
-                         frame)
-                      (wait-for-downlink-end #t)) ;; Got interference
-                     (($ <radio-event> 'downlink-end
-                         (= part-of-same-message? id)
-                         (= listening-to? chn)
-                         frame)
-                      (unless interference?
-                        (process-downlink! frame))) ;; TODO try RX2
-                     (_ (wait-for-downlink-end interference?))))))
-              ;; No preamble in time
-              ('time-is-out #f)
-              ;; Current message is not a preamble, continue
-              (_ (wait-for-downlink-start))))))
-      (put-message internal-com 'continue)))
+      (let* ((now       (get-internal-real-time))
+             (RX1-start (+ now (seconds->time-unit RECEIVE_DELAY1)))
+             (RX2-start (+ now (seconds->time-unit RECEIVE_DELAY2)))
+             (downlink  (or (begin (wait-until RX1-start)
+                                   (receive-window channel RX1))
+                            (if (< (get-internal-real-time) RX2-start)
+                              (begin (wait-until RX2-start)
+                                     (receive-window channel RX2))
+                              #f))))
+        (when downlink (process-downlink! downlink)))))
 
   (define (downstream-sink)
     (forever