diff --git a/DAS/simulator.py b/DAS/simulator.py
index b0902d9..5b60413 100644
--- a/DAS/simulator.py
+++ b/DAS/simulator.py
@@ -120,8 +120,7 @@ class Simulator:
             oldMissingSamples = missingSamples
             self.logger.debug("PHASE SEND %d" % steps, extra=self.format)
             for i in range(0,self.shape.numberValidators):
-                self.validators[i].sendRows()
-                self.validators[i].sendColumns()
+                self.validators[i].send()
             self.logger.debug("PHASE RECEIVE %d" % steps, extra=self.format)
             for i in range(1,self.shape.numberValidators):
                 self.validators[i].receiveRowsColumns()
diff --git a/DAS/validator.py b/DAS/validator.py
index 3270c38..89ca316 100644
--- a/DAS/validator.py
+++ b/DAS/validator.py
@@ -7,6 +7,17 @@ from DAS.block import *
 from bitarray import bitarray
 from bitarray.util import zeros
 
+def shuffled(lis):
+    # based on https://stackoverflow.com/a/60342323
+    for index in random.sample(range(len(lis)), len(lis)):
+        yield lis[index]
+
+class NextToSend:
+    def __init__(self, neigh, toSend, id, dim):
+        self.neigh = neigh
+        self.toSend = toSend
+        self.id = id
+        self.dim = dim
 
 class Neighbor:
     """This class implements a node neighbor to monitor sent and received data."""
@@ -55,8 +66,6 @@ class Validator:
                 #    random.seed(self.ID)
                 #self.rowIDs = random.sample(range(self.shape.blockSize), self.shape.chi)
                 #self.columnIDs = random.sample(range(self.shape.blockSize), self.shape.chi)
-        self.changedRow = {id:False for id in self.rowIDs}
-        self.changedColumn = {id:False for id in self.columnIDs}
         self.rowNeighbors = collections.defaultdict(dict)
         self.columnNeighbors = collections.defaultdict(dict)
 
@@ -66,6 +75,13 @@ class Validator:
         self.statsRxInSlot = 0
         self.statsRxPerSlot = []
 
+        # Set uplink bandwidth. In segments (~560 bytes) per timestep (50ms?)
+        # 1 Mbps ~= 1e6 / 20 / 8 / 560 ~= 11
+        # TODO: this should be a parameter
+        self.bwUplink = 1100 if not self.amIproposer else 22000 # approx. 100Mbps and 2Gbps
+
+        self.sched = self.nextToSend()
+
     def logIDs(self):
         """It logs the assigned rows and columns."""
         if self.amIproposer == 1:
@@ -99,9 +115,6 @@ class Validator:
                 else:
                     self.block.data[i] = 0
 
-            self.changedRow = {id:True for id in self.rowIDs}
-            self.changedColumn = {id:True for id in self.columnIDs}
-
             nbFailures = self.block.data.count(0)
             measuredFailureRate = nbFailures * 100 / (self.shape.blockSize * self.shape.blockSize)
             self.logger.debug("Number of failures: %d (%0.02f %%)", nbFailures, measuredFailureRate, extra=self.format)
@@ -144,16 +157,6 @@ class Validator:
             self.logger.debug("Receiving the data...", extra=self.format)
             #self.logger.debug("%s -> %s", self.block.data, self.receivedBlock.data, extra=self.format)
 
-            self.changedRow = { id:
-                self.getRow(id) != self.receivedBlock.getRow(id)
-                for id in self.rowIDs
-            }
-
-            self.changedColumn = { id:
-                self.getColumn(id) != self.receivedBlock.getColumn(id)
-                for id in self.columnIDs
-            }
-
             self.block.merge(self.receivedBlock)
 
             for neighs in self.rowNeighbors.values():
@@ -175,47 +178,92 @@ class Validator:
         self.statsTxInSlot = 0
 
 
-    def sendColumn(self, columnID):
-        """It sends any new sample in the given column."""
+    def nextColumnToSend(self, columnID):
         line = self.getColumn(columnID)
         if line.any():
             self.logger.debug("col %d -> %s", columnID, self.columnNeighbors[columnID] , extra=self.format)
-            for n in self.columnNeighbors[columnID].values():
+            for n in shuffled(list(self.columnNeighbors[columnID].values())):
 
                 # if there is anything new to send, send it
                 toSend = line & ~n.sent & ~n.received
                 if (toSend).any():
-                    n.sent |= toSend;
-                    n.node.receiveColumn(columnID, toSend, self.ID)
-                    self.statsTxInSlot += toSend.count(1)
+                    yield NextToSend(n, toSend, columnID, 1)
 
-    def sendRow(self, rowID):
-        """It sends any new sample in the given row."""
+    def nextRowToSend(self, rowID):
         line = self.getRow(rowID)
         if line.any():
             self.logger.debug("row %d -> %s", rowID, self.rowNeighbors[rowID], extra=self.format)
-            for n in self.rowNeighbors[rowID].values():
+            for n in shuffled(list(self.rowNeighbors[rowID].values())):
 
                 # if there is anything new to send, send it
                 toSend = line & ~n.sent & ~n.received
                 if (toSend).any():
-                    n.sent |= toSend;
-                    n.node.receiveRow(rowID, toSend, self.ID)
-                    self.statsTxInSlot += toSend.count(1)
+                    yield NextToSend(n, toSend, rowID, 0)
 
-    def sendRows(self):
-        """It sends all restored rows."""
-        self.logger.debug("Sending restored rows...", extra=self.format)
-        for r in self.rowIDs:
-            if self.changedRow[r]:
-                self.sendRow(r)
+    def nextToSend(self):
+        """ Send scheduler as a generator function
+        
+        Yields next segment(s) to send when asked for it.
+        Generates an infinite flow, returning with exit only when
+        there is nothing more to send.
 
-    def sendColumns(self):
-        """It sends all restored columns."""
-        self.logger.debug("Sending restored columns...", extra=self.format)
-        for c in self.columnIDs:
-            if self.changedColumn[c]:
-                self.sendColumn(c)
+        Generates a randomized order of columns and rows, sending to one neighbor
+        at each before sending to another neighbor.
+        Generates a new randomized ordering once all columns, rows, and neighbors
+        are processed once.
+        """
+
+        while True:
+            perLine = []
+            for c in self.columnIDs:
+                perLine.append(self.nextColumnToSend(c))
+
+            for r in self.rowIDs:
+                perLine.append(self.nextRowToSend(r))
+
+            count = 0
+            random.shuffle(perLine)
+            while (perLine):
+                for g in perLine.copy(): # we need a shallow copy to allow remove
+                    n = next(g, None)
+                    if not n:
+                        perLine.remove(g)
+                        continue
+                    count += 1
+                    yield n
+
+            # return if there is nothing more to send
+            if not count:
+                return
+
+    def send(self):
+        """ Send as much as we can in the timeslot, limited by bwUplink
+        """
+
+        for n in self.sched:
+            neigh = n.neigh
+            toSend = n.toSend
+            id = n.id
+            dim = n.dim
+
+            neigh.sent |= toSend;
+            if dim == 0:
+                neigh.node.receiveRow(id, toSend, self.ID)
+            else:
+                neigh.node.receiveColumn(id, toSend, self.ID)
+
+            sent = toSend.count(1)
+            self.statsTxInSlot += sent
+            self.logger.debug("sending %s %d to %d (%d)",
+                              "col" if dim else "row", id, neigh.node.ID, sent, extra=self.format)
+
+            # until we exhaust capacity
+            # TODO: use exact limit
+            if self.statsTxInSlot >self.bwUplink:
+                return
+
+        # Scheduler exited, nothing to send. Create new one for next round.
+        self.sched = self.nextToSend()
 
     def logRows(self):
         """It logs the rows assigned to the validator."""